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| Publications of April S. Brown :chronological alphabetical combined listing:%% Papers Published @booklet{Wu09, Author = {P. C. Wu and M. Losurdo and T. H. Kim and M. Giangregorio and G. Bruno and H. O. Everitt and A. S. Brown}, Title = {Plasmonic Gallium Nanoparticles on Polar Semiconductors: Interplay between Nanoparticle Wetting, Localized Surface Plasmon Dynamics, and Interface Charge}, Journal = {Langmuir}, Volume = {25}, Number = {2}, Pages = {924 -- 930}, Year = {2009}, Month = {January}, ISSN = {0743-7463}, Abstract = {Ga nanoparticles supported on large band gap semiconductors like SiC, GaN, and ZnO are interesting for plasmon-enhanced UV-emitting solid-state devices. We investigate the influence of the polarity of the SiC, GaN, and ZnO wurtzite semiconductors on the wetting of Ga nanoparticles and on the resulting surface plasmon resonance (SPR) by exploiting real time plasmonic ellipsometry. The interface potential between polar semiconductors (SiC, GaN, and ZnO) and plasmonic nanoparticles (gallium) is shown to influence nanoparticle formation dynamics, geometry, and consequently the SPR wavelength. We invoke the Lippman electrowetting framework to elucidate the mechanisms controlling nanoparticle dynamics and experimentally demonstrate that the charge transfer at the Ga nanoparticle/polar semiconductor interface is an intrinsic method for tailoring the nanoparticle plasmon resonance. Therefore, the present data demonstrate that for supported nanoparticles, surface and interface piezoelectric charge of polar semiconductors also affects SPR along with the well-known effect of the media refractive index.}, Key = {Wu09} } @booklet{Garcia08, Author = {M. A. Garcia and M. Losurdo and S. D. Wolter and W. V. Lampert and J. Bonaventura and G. Bruno and C. Yi and A. S. Brown}, Title = {Comparison of Functionalized III-V Semiconductor Response for Nitric Oxide}, Journal = {Sensor Letters}, Volume = {6}, Number = {4}, Pages = {627 -- 634}, Year = {2008}, Month = {August}, ISSN = {1546-198X}, Abstract = {Several III-V materials systems, consisting of InAs, InP, and GaN, were chemically functionalized, characterized, and evaluated for Nitric Oxide (NO) sensor research. The hemin porphyrin has been a particularly successful NO detection functional group for carbon-based material systems for sensors. The unique sensing modalities inherent in an InAs surface accumulation layer and the AlGaN/GaN surface polarization charge coupling motivated enhanced chemical sensor exploration. NO's diverse roles in defense, biological, and environmental fields create interest in the development of responsive and selective solid state sensors. In a controlled gaseous environment, functionalized and pre-functionalized III-V semiconductor materials were probed for changes in resistivity during exposure to varying concentrations of NO, NO2, O-2 and Ar. X-ray photoelectron spectroscopy was used to characterize sample functionalization and analyte influences on the valence band maxima in order to better understand the charge transduction mechanisms. The results of the trials were compared and analyzed for optimization and materials recommendations.}, Key = {Garcia08} } @booklet{Losurdo07, Author = {M. Losurdo and M. M. Giangregorio and G. Bruno and T. H. Kim and S. Choi and A. S. Brown and G. Pettinari and M. Capizzi and A. Polimeni}, Title = {Behavior of hydrogen in InN investigated in real time exploiting spectroscopic ellipsometry}, Journal = {Applied Physics Letters}, Volume = {91}, Number = {8}, Year = {2007}, Month = {August}, ISSN = {0003-6951}, Abstract = {The interaction of hydrogen with InN epitaxial films has been investigated by exposing InN to a remote hydrogen plasma and monitoring changes in the InN optical properties in real time via spectroscopic ellipsometry. Atomic hydrogen reacts swith InN causing nitrogen depletion with formation of indium clusters at the sample surface. After terminating the hydrogenation process, the hydrogen remains stable in the InN host lattice at T $<$ 200 degrees C, while at higher temperatures it partially desorbs as NHx and InHx (x=1-3).}, Key = {Losurdo07} } @booklet{Mckay07, Author = {K. S. Mckay and F. P. Lu and J. Kim and C. H. Yi and A. S. Brown and A. R. Hawkins}, Title = {Band discontinuity measurements of the wafer bonded InGaAs/Si heterojunction}, Journal = {Applied Physics Letters}, Volume = {90}, Number = {22}, Year = {2007}, Month = {May}, ISSN = {0003-6951}, Abstract = {p-type InGaAs/Si heterojunctions were fabricated through a wafer fusion bonding process. The relative band alignment between the two materials at the heterointerface was determined using current-voltage (I-V) measurements and applying thermionic emission-diffusion theory. The valence and conduction band discontinuities for the InGaAs/Si interface were determined to be 0.48 and -0.1 eV, respectively, indicating a type-II band alignment. (C) 2007 American Institute of Physics.}, Key = {Mckay07} } @booklet{Uhlrich07, Author = {J. Uhlrich and M. Garcia and S. Wolter and A. S. Brown and T. F. Kuech}, Title = {Interfacial chemistry and energy band line-up of pentacene with the GaN (0001) surface}, Journal = {Journal Of Crystal Growth}, Volume = {300}, Number = {1}, Pages = {204 -- 211}, Year = {2007}, Month = {March}, ISSN = {0022-0248}, Abstract = {The chemical nature of the GaN surface combined with the bulk and surface electronic structure opens new potential application areas for this material. The nature of specific organic-GaN was developed for two cases in which the surface electronic structure of such interfaces was developed and utilized. The band alignment between n-GaN and pentacene was determined for surfaces prepared through reaction with HCl. The energy band offset was estimated through combined X-ray photoelectron spectroscopy and ultraviolet photoemission measurements. XPS measurements indicated that there was no interfacial chemical reaction. The measured valence band offset between the n-GaN and the vapor-deposited pentacene was estimated to be greater than 2 eV providing a favorable band-offset for hole-injection from the GaN layer into pentacene. The surface of a AlGaN/GaN heterojunction field effect transistor (HFET) structures was also functionalized by an adsorbed hemin layer and was shown to be sensitive to the presence of reactive species such as NO. The HFET structure provides enhanced sensitivity to changes in the surface electric field, altered through the adsorption of chemically active species either directly on the surface or through the interactions with surface functionalization. (c) 2006 Elsevier B.V. All rights reserved.}, Key = {Uhlrich07} } @booklet{Wu07a, Author = {P. C. Wu and T. H. Kim and A. S. Brown and M. Losurdo and G. Bruno and H. O. Everitt}, Title = {Real-time plasmon resonance tuning of liquid Ga nanoparticles by in situ spectroscopic ellipsometry}, Journal = {Applied Physics Letters}, Volume = {90}, Number = {10}, Year = {2007}, Month = {March}, ISSN = {0003-6951}, Abstract = {Liquid Ga nanoparticles have been deposited on sapphire substrates at room temperature. The optical evolution of Ga nanoparticle surface plasmon resonance during deposition has been characterized by in situ real-time spectroscopic ellipsometry to control and tune the plasmon resonance photon energy. The existence of both longitudinal and transverse modes for spheroidal Ga nanoparticles supported on a sapphire substrate is demonstrated and the dependence of the longitudinal and transverse plasmon energies on particle size is discussed. Stability of the Ga surface plasmon resonance to air exposure and high temperature is also demonstrated. (c) 2007 American Institute of Physics.}, Key = {Wu07a} } @article{070910462413, Author = {Uhlrich, J. and Garcia, M. and Wolter, S. and Brown, A.S. and Kuech, T.F.}, Title = {Interfacial chemistry and energy band line-up of pentacene with the GaN (0 0 0 1) surface}, Journal = {Journal of Crystal Growth}, Volume = {300}, Number = {1}, Pages = {204 - 211}, Year = {2007}, url = {http://dx.doi.org/10.1016/j.jcrysgro.2006.11.035}, Keywords = {Band structure;Gallium nitride;Interfaces (materials);Junction gate field effect transistors;Metallorganic vapor phase epitaxy;Reaction kinetics;Surface chemistry;X ray photoelectron spectroscopy;}, Abstract = {The chemical nature of the GaN surface combined with the bulk and surface electronic structure opens new potential application areas for this material. The nature of specific organic-GaN was developed for two cases in which the surface electronic structure of such interfaces was developed and utilized. The band alignment between n-GaN and pentacene was determined for surfaces prepared through reaction with HCl. The energy band offset was estimated through combined X-ray photoelectron spectroscopy and ultraviolet photoemission measurements. XPS measurements indicated that there was no interfacial chemical reaction. The measured valence band offset between the n-GaN and the vapor-deposited pentacene was estimated to be greater than 2 eV providing a favorable band-offset for hole-injection from the GaN layer into pentacene. The surface of a AlGaN/GaN heterojunction field effect transistor (HFET) structures was also functionalized by an adsorbed hemin layer and was shown to be sensitive to the presence of reactive species such as NO. The HFET structure provides enhanced sensitivity to changes in the surface electric field, altered through the adsorption of chemically active species either directly on the surface or through the interactions with surface functionalization. © 2006 Elsevier B.V. All rights reserved.}, Key = {070910462413} } @article{071110490609, Author = {Wu, Pae C and Kim, Tong-Ho and Brown, April S. and Losurdo, Maria and Bruno, Giovanni and Everitt, Henry O.}, Title = {Real-time plasmon resonance tuning of liquid Ga nanoparticles by in situ spectroscopic ellipsometry}, Journal = {Applied Physics Letters}, Volume = {90}, Number = {10}, Pages = {103119 -}, Year = {2007}, url = {http://dx.doi.org/10.1063/1.2712508}, Keywords = {Gallium compounds;Particle size;Real time systems;Sapphire;Spectroscopic ellipsometry;Surface plasmon resonance;}, Abstract = {Liquid Ga nanoparticles have been deposited on sapphire substrates at room temperature. The optical evolution of Ga nanoparticle surface plasmon resonance during deposition has been characterized by in situ real-time spectroscopic ellipsometry to control and tune the plasmon resonance photon energy. The existence of both longitudinal and transverse modes for spheroidal Ga nanoparticles supported on a sapphire substrate is demonstrated and the dependence of the longitudinal and transverse plasmon energies on particle size is discussed. Stability of the Ga surface plasmon resonance to air exposure and high temperature is also demonstrated. © 2007 American Institute of Physics.}, Key = {071110490609} } @booklet{Yoon07, Author = {I. Yoon and C. Yi and T. Kirn and A. S. Brown and A. Seabaugh}, Title = {Effect of surface pretreatment and substrate orientation on the characteristics of InAs quantum dots on Si and SiO2 substrates}, Journal = {Journal Of Vacuum Science \& Technology B}, Volume = {25}, Number = {3}, Pages = {945 -- 947}, Year = {2007}, ISSN = {1071-1023}, Abstract = {The surface m orphology of InAs quantum dots (QDs) on undoped Si (100) shows a strong dependency on surface pretreatments, with as much as 30\% difference in island density with different size distributions. Lowering the V/III fluxes ratio (5 8: 1 to 10: 1) effectively suppresses the average height (47\%) and increases density (75\%) of QDs. While changing the growth temperature (220-300 degrees C) increased the average height by 62\% on chemically etched Si surfaces, nucleation on the SiO2 surface was less sensitive to surface preparation. The authors alsd observe that the specific substrate orientation and annealing at 500 degrees C do not significantly impact the morphology of QDs. (c) 2007 American Vacuum Society.}, Key = {Yoon07} } @booklet{Wu07, Author = {P. C. Wu and M. Losurdo and T. H. Kim and O. Choi and G. Bruno and A. S. Brown}, Title = {In situ spectroscopic ellipsometry to monitor surface plasmon resonant group-III metals deposited by molecular beam epitaxy}, Journal = {Journal Of Vacuum Science \& Technology B}, Volume = {25}, Number = {3}, Pages = {1019 -- 1023}, Year = {2007}, ISSN = {1071-1023}, Abstract = {The evolution of the surface plasmon resonance of Al, Ga, and In deposited by molecular beam epitaxy on GaN surfaces was monitored in real-time using spectroscopic ellipsometry. The correlation between the metal plasmon resonance modes, the particle size, and the growth mode is addressed. Gaand In deposited on GaN substrates form nanoparticles while the Al is shown to form a nearly coalesced thin film. The plasmon resonance of the Ga and In nanoparticles redshift with increasing average particle size while the pseudodielectric function of Al approaches that of a Drude metal. (c) 2007 American Vacuum Society.}, Key = {Wu07} } @booklet{Bruno06, Author = {G. Bruno and M. Losurdo and M. M. Giangregorio and P. Capezzuto and A. S. Brown and T. H. Kim and S. Choi}, Title = {Real time ellipsometry for monitoring plasma-assisted epitaxial growth of GaN}, Journal = {Applied Surface Science}, Volume = {253}, Number = {1}, Pages = {219 -- 223}, Year = {2006}, Month = {October}, ISSN = {0169-4332}, Abstract = {GaN is grown on Si-face 4H-SiC(001) substrates using remote plasma-assisted methods including metalorganic chemical vapour deposition (RP-MOCVD) and molecular beam epitaxy (MBE). Real time spectroscopic ellipsometry is used for monitoring all the steps of substrate pre-treatments and the heteroepitaxial growth of GaN on SiC. Our characterization emphasis is on understanding the nucleation mechanism and the GaN growth mode, which depend on the SiC surface preparation. (c) 2006 Elsevier B.V. All rights reserved.}, Key = {Bruno06} } @booklet{Morse06, Author = {M. Morse and P. Wu and S. Choi and T. H. Kim and A. S. Brown and M. Losurdo and G. Bruno}, Title = {Structural and optical characterization of GaN heteroepitaxial films on SiC substrates}, Journal = {Applied Surface Science}, Volume = {253}, Number = {1}, Pages = {232 -- 235}, Year = {2006}, Month = {October}, ISSN = {0169-4332}, Abstract = {We have estimated the threading dislocation density and type via X-ray diffraction and Williamson-Hall analysis to elicit qualitative information directly related to the electrical and optical quality of GaN epitaxial layers grown by PAMBE on 4H- and 6H-SiC substrates. The substrate surface preparation and buffer choice, specifically: Ga flashing for SiC oxide removal, controlled nitridation of SiC, and use of AlN buffer layers all impact the resultant screw dislocation density, but do not significantly influence the edge dislocation density. We show that modification of the substrate surface strongly affects the screw dislocation density, presumably due to impact on nucleation during the initial stages of heteroepitaxy. (c) 2006 Published by Elsevier B.V.}, Key = {Morse06} } @booklet{Yi06, Author = {C. H. Yi and T. H. Kim and A. S. Brown}, Title = {InAs-based p-n homojunction diodes: Doping effects and impact of doping on device parameters}, Journal = {Journal Of Electronic Materials}, Volume = {35}, Number = {9}, Pages = {1712 -- 1714}, Year = {2006}, Month = {September}, ISSN = {0361-5235}, Abstract = {InAs heterojunction bipolar transistors (HBTs) are promising candidates for low power and high frequency (THz) device applications due to their small bandgap, high electron mobility, and high saturation drift velocity. However, doping limits such as the trade-off between desired low intentional n-type concentrations and unintentional doping, and the realization of high p-type concentrations, must still be considered in device design and synthesis. In order to observe the impact of intentional and unintentional n-type doping on diode electrical properties, InAs-based homojunction diodes have been grown on InAs substrates by solid-source molecular beam epitaxy (SSMBE) and were subsequently fabricated and characterized.}, Key = {Yi06} } @booklet{Triplett06, Author = {G. E. Triplett and A. S. Brown and G. S. May}, Title = {Strain monitoring in InAs-AlxGa1-xAsySb1-y structures grown by molecular beam epitaxy}, Journal = {Applied Physics Letters}, Volume = {89}, Number = {3}, Pages = {345 -- 349}, Year = {2006}, Month = {July}, ISSN = {0003-6951}, Abstract = {A study of strained InAs-AlxGa1-xAsySb1-y quantum well structures produced by molecular beam epitaxy is presented. The ability to manipulate quantum well strain by way of the AlxGa1-xAsySb1-y buffer is examined using statistical experimental design. Results show that anion composition in the buffer (with a target lattice constant, a=6.12 angstrom) varies by as much as 3\% in the 450-500 degrees C growth temperature range. The data reveal interrelationships between strain, structural characteristics, and conductivity. Results demonstrate that these relationships exist and can be modeled empirically and exploited for the design of near-infrared optoelectronic devices. (c) 2006 American Institute of Physics.}, Key = {Triplett06} } @booklet{Losurdo06, Author = {M. Losurdo and P. Capezzuto and G. Bruno and A. S. Brown and T. Brown and G. May}, Title = {Fundamental reactions controlling anion exchange during mixed anion heterojunction formation: Chemistry of As-for-Sb and Sb-for-As exchange reactions}, Journal = {Journal Of Applied Physics}, Volume = {100}, Number = {1}, Year = {2006}, Month = {July}, ISSN = {0021-8979}, Abstract = {As-for-Sb and Sb-for-As anion exchange reactions have been investigated by the exposure of GaSb surfaces to As-2 and As-4 species and by the exposure of GaAs to Sb-2, respectively. The effect of surface temperature, anion soak time, and anion species (either As-2 or As-4) on the chemistry governing the anion exchange reactions during GaAsySb1-y/GaSb and GaSbyAs1-y/GaAs heterostructure formation by molecular beam epitaxy is examined. It is found that when GaSb surfaces are exposed to arsenic, the anion exchange reaction competes with the formation of isoelectronic compounds, AsSby, which form clusters precipitating in the GaAsySb1-y/GaSb heterostructures. The relative amount of GaAs and AsSby depends on the surface temperature, the As soak time, and on the As species, i.e., As-2 or As-4. We observe specific process conditions that minimize AsSby formation, yielding more abrupt heterojunction interfaces. In the case of the Sb-2/GaAs system, the Sb-for-As anion exchange does not occur to a significant degree, but surface segregation of antimony is found. A chemical model for the As-for-Sb anion exchange reaction is proposed. (c) 2006 American Institute of Physics.}, Key = {Losurdo06} } @booklet{Kim06, Author = {T. H. Kim and S. Choi and A. S. Brown and M. Losurdo and G. Bruno}, Title = {Impact of 4H- and 6H-SiC(0001) nitridation on Ga wetting layer development and GaN growth by molecular beam epitaxy}, Journal = {Applied Physics Letters}, Volume = {89}, Number = {2}, Year = {2006}, Month = {July}, ISSN = {0003-6951}, Abstract = {GaN epitaxial layers have been grown by plasma-assisted molecular beam epitaxy on Si-face 4H- and 6H-SiC(0001)(Si) substrates. The impact of the SiC surface preparation and oxide removal achieved via a Ga flash-off process followed by nitridation on the structure and properties of GaN epitaxial layers is articulated. A correlation among the SiC surface nitridation conditions, the Ga wetting layer development, the nucleation layer, and GaN crystalline properties is revealed. (c) 2006 American Institute of Physics.}, Key = {Kim06} } @booklet{Brown06, Author = {A. S. Brown and M. Losurdo and P. Capezzuto and G. Bruno and T. Brown and G. May}, Title = {Fundamental reactions controlling anion exchange during mixed anion heterojunction formation: Chemistry and kinetics of P-for-As exchange reaction}, Journal = {Journal Of Applied Physics}, Volume = {99}, Number = {9}, Year = {2006}, Month = {May}, ISSN = {0021-8979}, Abstract = {The fundamental chemical and kinetic surface processes governing the P-for-As exchange reaction during epitaxial layer synthesis are investigated. Exposure of a GaAs surface to phosphorus molecular beams (P-2) is carried out to create superlattice structures realized by surface reactions. The impact of the GaAs surface reconstruction, the P-soak time, and the surface temperature on the extent of intermixing and on the mechanism governing the anion exchange has been studied using x-ray diffraction, spectroscopic ellipsometry, x-ray photoelectron spectroscopy, and atomic force microscopy. It is found that As-rich GaAs surface reconstructions inhibit P-for-As exchange. The extent of the anion exchange increases with temperature. Furthermore, the P-for-As exchange is not controlled by P diffusion into the GaAs. We propose a chemical model that includes P chemisorption and indiffusion, and the competition between P-for-As anion exchange and the formation of AsP isoelectronic compounds. (C) 2006 American Institute of Physics.}, Key = {Brown06} } @booklet{Triplett06a, Author = {G. E. Triplett and A. S. Brown and G. S. May}, Title = {Interrelationships in the electronic and structural characteristics of strained InAs quantum well structures}, Journal = {Journal Of Crystal Growth}, Volume = {286}, Number = {2}, Pages = {345 -- 349}, Year = {2006}, Month = {January}, ISSN = {0022-0248}, Abstract = {Indium-arsenide (InAs)-based devices are promising for next generation electronic and optoelectronic applications. Improving these devices requires greater control of the InAs quantum well properties, which in part, are related to the strain induced from the substrate material, buffer layer thickness, barrier composition, doping, and the heterointerface. This report focuses on the latter and includes X-ray diffraction and Hall results from a statistical experimental design (SED), which focused on the growth sequence at the heterointerface and growth throughout the channel, and illuminates correlations between structural variations and the electronic properties in strained InAs quantum well structures produced by molecular beam epitaxy (MBE). This data suggest that as more antimony from the sublayer is incorporated in the InAs layer, a product of anion exchange between antimony surface atoms and ensuing arsenic flux atoms, the strain states vary along with InAs channel mobility. (c) 2005 Elsevier B.V. All rights reserved.}, Key = {Triplett06a} } @article{063110037506, Author = {Brown, April S. and Kim, Tong-Ho and Choi, Soojeong and Wu, Pae and Morse, Michael and Losurdo, Maria and Giangregorio, Maria M. and Bruno, Giovanni and Moto, Akihiro}, Title = {Growth of InN on 6H-SiC by plasma assisted molecular beam epitaxy}, Journal = {Physica Status Solidi C: Current Topics in Solid State Physics}, Volume = {3}, Pages = {1531 - 1535}, Address = {Bremen, Germany}, Year = {2006}, url = {http://dx.doi.org/10.1002/pssc.200565150}, Keywords = {Semiconducting silicon compounds;Molecular beam epitaxy;Epitaxial growth;Annealing;Ellipsometry;Electric properties;Optical properties;}, Abstract = {We have investigated the growth of InN films by plasma assisted molecular beam epitaxy on the Si-face of 6H-SiC(0001). Growth is performed under In-rich conditions using a two-step process consisting of the deposition of a thin, low-temperature 350°C InN buffer layer, followed by the subsequent deposition of the InN epitaxial layer at 450°C. The effect of buffer annealing is investigated. The structural and optical evolution of the growing layer has been monitored in real time using RHEED and spectroscopic ellipsometry. Structural, morphological, electrical and optic properties are discussed. © 2006 WILEY-VCH Verlag GmbH and Co. KGaA.}, Key = {063110037506} } @article{06229911078, Author = {Brown, April S. and Losurdo, Maria and Capezzuto, Pio and Bruno, Giovanni and Brown, Terence and May, Gary}, Title = {Fundamental reactions controlling anion exchange during mixed anion heterojunction formation: Chemistry and kinetics of P-for-As exchange reaction}, Journal = {Journal of Applied Physics}, Volume = {99}, Number = {9}, Pages = {093510 -}, Year = {2006}, url = {http://dx.doi.org/10.1063/1.2194126}, Keywords = {Reaction kinetics;Surface properties;Epitaxial growth;Superlattices;Semiconducting gallium compounds;X ray diffraction analysis;Ellipsometry;X ray photoelectron spectroscopy;Ion exchange;Chemisorption;}, Abstract = {The fundamental chemical and kinetic surface processes governing the P-for-As exchange reaction during epitaxial layer synthesis are investigated. Exposure of a GaAs surface to phosphorus molecular beams (P2) is carried out to create superlattice structures realized by surface reactions. The impact of the GaAs surface reconstruction, the P-soak time, and the surface temperature on the extent of intermixing and on the mechanism governing the anion exchange has been studied using x-ray diffraction, spectroscopic ellipsometry, x-ray photoelectron spectroscopy, and atomic force microscopy. It is found that As-rich GaAs surface reconstructions inhibit P-for-As exchange. The extent of the anion exchange increases with temperature. Furthermore, the P-for-As exchange is not controlled by P diffusion into the GaAs. We propose a chemical model that includes P chemisorption and indiffusion, and the competition between P-for-As anion exchange and the formation of AsP isoelectronic compounds. © 2006 American Institute of Physics.}, Key = {06229911078} } @article{06019623333, Author = {Triplett, Gregory Edward and Brown, April S. and May, Gary S.}, Title = {Interrelationships in the electronic and structural characteristics of strained InAs quantum well structures}, Journal = {Journal of Crystal Growth}, Volume = {286}, Number = {2}, Pages = {345 - 349}, Year = {2006}, url = {http://dx.doi.org/10.1016/j.jcrysgro.2005.10.098}, Keywords = {Semiconducting indium compounds;Optoelectronic devices;Strain;Semiconductor doping;Hall effect;X ray diffraction;Ion exchange;Molecular beam epitaxy;}, Abstract = {Indium-arsenide (InAs)-based devices are promising for next generation electronic and optoelectronic applications. Improving these devices requires greater control of the InAs quantum well properties, which in part, are related to the strain induced from the substrate material, buffer layer thickness, barrier composition, doping, and the heterointerface. This report focuses on the latter and includes X-ray diffraction and Hall results from a statistical experimental design (SED), which focused on the growth sequence at the heterointerface and growth throughout the channel, and illuminates correlations between structural variations and the electronic properties in strained InAs quantum well structures produced by molecular beam epitaxy (MBE). This data suggest that as more antimony from the sublayer is incorporated in the InAs layer, a product of anion exchange between antimony surface atoms and ensuing arsenic flux atoms, the strain states vary along with InAs channel mobility. © 2005 Elsevier B.V. All rights reserved.}, Key = {06019623333} } @article{063010023324, Author = {Kim, Tong-Ho and Choi, Soojeong and Brown, April S. and Losurdo, Maria and Bruno, Giovanni}, Title = {Impact of 4H- And 6H-SiC(0001) nitridation on Ga wetting layer development and GaN growth by molecular beam epitaxy}, Journal = {Applied Physics Letters}, Volume = {89}, Number = {2}, Pages = {021916 -}, Year = {2006}, url = {http://dx.doi.org/10.1063/1.2220007}, Keywords = {Gallium nitride;Epitaxial growth;Oxides;Nucleation;Molecular beam epitaxy;}, Abstract = {GaN epitaxial layers have been grown by plasma-assisted molecular beam epitaxy on Si-face 4H-and 6H-SiC(0001)<sub>Si</sub> substrates. The impact of the SiC surface preparation and oxide removal achieved via a Ga flash-off process followed by nitridation on the structure and properties of GaN epitaxial layers is articulated. A correlation among the SiC surface nitridation conditions, the Ga wetting layer development, the nucleation layer, and GaN crystalline properties is revealed. © 2006 American Institute of Physics.}, Key = {063010023324} } @article{064510222023, Author = {Bruno, Giovanni and Losurdo, Maria and Giangregorio, Maria M. and Capezzuto, Pio and Brown, April S. and Kim, Tong-Ho and Choi, Soojeong}, Title = {Real time ellipsometry for monitoring plasma-assisted epitaxial growth of GaN}, Journal = {Applied Surface Science}, Volume = {253}, Number = {1 SPEC ISS}, Pages = {219 - 223}, Year = {2006}, url = {http://dx.doi.org/10.1016/j.apsusc.2006.05.129}, Keywords = {Ellipsometry;Epitaxial growth;Silicon carbide;Plasma applications;Metallorganic chemical vapor deposition;Nucleation;}, Abstract = {GaN is grown on Si-face 4H-SiC(0 0 0 1) substrates using remote plasma-assisted methods including metalorganic chemical vapour deposition (RP-MOCVD) and molecular beam epitaxy (MBE). Real time spectroscopic ellipsometry is used for monitoring all the steps of substrate pre-treatments and the heteroepitaxial growth of GaN on SiC. Our characterization emphasis is on understanding the nucleation mechanism and the GaN growth mode, which depend on the SiC surface preparation. © 2006 Elsevier B.V. All rights reserved.}, Key = {064510222023} } @article{064510222017, Author = {Morse, M. and Wu, P. and Choi, S. and Kim, T.H. and Brown, A.S. and Losurdo, M. and Bruno, G.}, Title = {Structural and optical characterization of GaN heteroepitaxial films on SiC substrates}, Journal = {Applied Surface Science}, Volume = {253}, Number = {1 SPEC ISS}, Pages = {232 - 235}, Year = {2006}, url = {http://dx.doi.org/10.1016/j.apsusc.2006.05.097}, Keywords = {Gallium nitride;Silicon carbide;Optical properties;X ray diffraction;Dislocations (crystals);Nucleation;}, Abstract = {We have estimated the threading dislocation density and type via X-ray diffraction and Williamson-Hall analysis to elicit qualitative information directly related to the electrical and optical quality of GaN epitaxial layers grown by PAMBE on 4H- and 6H-SiC substrates. The substrate surface preparation and buffer choice, specifically: Ga flashing for SiC oxide removal, controlled nitridation of SiC, and use of AlN buffer layers all impact the resultant screw dislocation density, but do not significantly influence the edge dislocation density. We show that modification of the substrate surface strongly affects the screw dislocation density, presumably due to impact on nucleation during the initial stages of heteroepitaxy. © 2006.}, Key = {064510222017} } @article{063010033806, Author = {Triplett, Gregory E. and Brown, April S. and May, Gary S.}, Title = {Strain monitoring in InAs-AlxGa1-xAS ySb1-y structures grown by molecular beam epitaxy}, Journal = {Applied Physics Letters}, Volume = {89}, Number = {3}, Pages = {032106 -}, Year = {2006}, url = {http://dx.doi.org/10.1063/1.2226998}, Keywords = {Semiconductor quantum wells;Molecular beam epitaxy;Statistical methods;Negative ions;Strain;Optoelectronic devices;}, Abstract = {A study of strained InAs-Al<sub>x</sub>Ga<sub>1-x</sub>As <sub>y</sub>Sb<sub>1-y</sub> quantum well structures produced by molecular beam epitaxy is presented. The ability to manipulate quantum well strain by way of the Al<sub>x</sub>Ga<sub>1-x</sub>As<sub>y</sub>Sb<sub>1-y</sub> buffer is examined using statistical experimental design. Results show that anion composition in the buffer (with a target lattice constant, a=6.12 A) varies by as much as 3% in the 450-500°C growth temperature range. The data reveal interrelationships between strain, structural characteristics, and conductivity. Results demonstrate that these relationships exist and can be modeled empirically and exploited for the design of near-infrared optoelectronic devices. © 2006 American Institute of Physics.}, Key = {063010033806} } @article{064110158746, Author = {Yi, Changhyun and Kim, Tong-Ho and Brown, April S.}, Title = {InAs-based p-n homojunction diodes: Doping effects and impact of doping on device parameters}, Journal = {Journal of Electronic Materials}, Volume = {35}, Number = {9}, Pages = {1712 - 1714}, Year = {2006}, Keywords = {Semiconducting indium compounds;Semiconductor doping;Heterojunction bipolar transistors;Electron mobility;Product design;Electric properties;Molecular beam epitaxy;}, Abstract = {InAs heterojunction bipolar transistors (HBTs) are promising candidates for low power and high frequency (THz) device applications due to their small bandgap, high electron mobility, and high saturation drift velocity. However, doping limits such as the trade-off between desired low intentional n-type concentrations and unintentional doping, and the realization of high p-type concentrations, must still be considered in device design and synthesis. In order to observe the impact of intentional and unintentional n-type doping on diode electrical properties, InAs-based homojunction diodes have been grown on InAs substrates by solid-source molecular beam epitaxy (SSMBE) and were subsequently fabricated and characterized.}, Key = {064110158746} } @article{05209101122, Author = {Losurdo, Maria and Giangregorio, Maria M. and Capezzuto, Pio and Bruno, Giovanni and Brown, April S. and Kim, Tong-Ho and Yi, Changhyun}, Title = {Modification of 4H-SiC and 6H-SiC(0001)Si surfaces through the interaction with atomic hydrogen and nitrogen}, Journal = {Journal of Electronic Materials}, Volume = {34}, Number = {4}, Pages = {457 - 465}, Year = {2005}, Keywords = {Surface chemistry;Hydrogen;Nitrogen;Hydrogenation;Plasma applications;Reaction kinetics;X ray photoelectron spectroscopy;Atomic force microscopy;Thermal effects;Passivation;Crystal orientation;Energy gap;Epitaxial growth;Geometry;}, Abstract = {The interaction of 4H-SiC(0001)<sub>Si</sub> and 6H-SiC(0001)<sub>Si</sub> surfaces with atomic hydrogen and atomic nitrogen produced by remote radio-frequency plasmas is investigated. The kinetics of the surface modifications is monitored in real time using ellipsometry, while chemical modifications of the surface are characterized using x-ray photoelectron spectroscopy (XPS). Film morphological properties are assessed with atomic force microscopy (AFM). A two-stage sub-strate preparation procedure is described that effectively removes oxygen from the SiC surface at low (200°C) temperature. In the first step, the SiC surface is etched with an HCl/HF acid solution as an alternative to the conventional HF(1%)-H<sub>2</sub>O solution. The HCl/HF etch provides effective hydrogen passivation of the SiC surface. In the second step, the SiC surface is exposed to atomic hydrogen that selectively interacts with residual oxygen. In addition, the temperature dependence of the nitridation of SiC surfaces has also been investigated. It is found that interaction of SiC surfaces with atomic hydrogen at 200°C provides clean, smooth, and terraced surfaces suitable for epitaxial growth. In contrast, SiC surface exposure at high temperature (750°C) to atomic hydrogen and nitrogen results in very rough and disordered Si-rich surfaces. Finally, we find that the 4H-SiC surface is more reactive than the 6H-SiC surface to both species studied, independent of temperature. Surface geometry and electronic factors responsible for the observed reactivities are discussed.}, Key = {05209101122} } @article{05479486792, Author = {Brown, A.S. and Losurdo, M. and Kim, T.H. and Giangregorio, M.M. and Choi, S. and Morse, M. and Wu, P. and Capezzuto, P. and Bruno, G.}, Title = {The impact of SiC substrate treatment on the heteroepitaxial growth of GaN by plasma assisted MBE}, Journal = {Crystal Research and Technology}, Volume = {40}, Number = {10-11}, Pages = {997 - 1002}, Year = {2005}, url = {http://dx.doi.org/10.1002/crat.200410475}, Keywords = {Epitaxial growth;Semiconducting gallium arsenide;Nitrides;Nucleation;X ray photoelectron spectroscopy;Atomic force microscopy;Spectroscopic analysis;Surface treatment;}, Abstract = {We report on the impact of the preparation of the Si-face 4H-SiC(0001) <sub>Si</sub> substrate using a Ga flash-off process on the epitaxial growth of GaN by plasma-assisted molecular beam epitaxy. The nucleation, as well as the resultant structural and morphological properties of GaN grown directly on 4H-SiC(0001)<sub>Si</sub> are strongly influenced by the chemical and morphological modifications of the SiC surface induced by the Ga flash-off process. Herein we describe the impact of the specific concentration of Ga incident on the surface (quantified in terms of monolayer (ML) coverage): of 0.5 ML, 1ML and 2ML. The residual oxygen at the SiC surface, unintentional SiC nitridation and the formation of cubic GaN grains during the initial nucleation stage, are all reduced when a 2 ML Ga flash is used. All of the above factors result in structural improvement of the GaN epitaxial layers. The correlation between the SiC surface modification, the initial nucleation stage, and the GaN epitaxial layer structural quality has been articulated using x-ray photoelectron spectroscopy, x-ray diffraction, atomic force microscopy and spectroscopic ellipsometry data. © 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim.}, Key = {05479486792} } @article{05319271476, Author = {Collins, Leslie M. and Huettel, Lisa G. and Brown, April S. and Ybarra, Gary A. and Holmes, Joseph S. and Board, John A. and Cummer, Steven A. and Gustafson, Michael R. and Kim, Jungsang and Massoud, Hisham Z.}, Title = {Theme-based redesign of the duke university ECE curriculum: The first steps}, Journal = {ASEE Annual Conference and Exposition, Conference Proceedings}, Pages = {14313 - 14326}, Address = {Portland, OR, United States}, Year = {2005}, Keywords = {Students;Curricula;Planning;Data processing;Electronic equipment;Benchmarking;}, Abstract = {Undergraduates in Electrical and Computer Engineering (ECE) at Duke University have benefited from the combination of curricular flexibility and rigorous coursework. The current curriculum is further limited in that the core courses do not offer a vertically integrated thematic introduction to ECE as a discipline nor are they reflective of the broader scope of ECE field of study. The course has streamlined structure, which is consistent with an educational theme. Results from Educational BEnchmark Inc. (EBI) survey of students confirmed that they too perceive the oppurtinities for improvement in curriculum.}, Key = {05319271476} } @article{05299222741, Author = {Seo, Sang-Woo and Cho, Sang-Yeon and Huang, Sa and Jokerst, Nan Marie and Brown, April S.}, Title = {Pulse response tuning of high speed InGaAs thin film MSM photodetector using external RCL loads}, Journal = {Proceedings of SPIE - The International Society for Optical Engineering}, Volume = {5726}, Pages = {52 - 60}, Address = {San Jose, CA, United States}, Year = {2005}, url = {http://dx.doi.org/10.1117/12.592246}, Keywords = {Semiconducting indium gallium arsenide;Thin film devices;Frequency response;Semiconducting films;Light transmission;Microwaves;Digital communication systems;Natural frequencies;Inductance;Capacitance;Millimeter waves;}, Abstract = {Practical, packaged photodetectors (PDs) must be interfaced to bias and transmission lines, which introduce parasitics. These parasitics (resistance, capacitance and inductance) can be used to shape the temporal and frequency response of packaged photodetectors. Thus, the bias circuitry, external passives, and high speed interconnections must be carefully designed to produce the desired response in a packaged photodetector. Applications dictate the desired PD characteristics, which are generally either a flat frequency response, or a fast, ring-free impulse response. In this paper, the effects of the parasitic resistance, capacitance, and inductance are studied to affect the intrinsic response of photodetectors for a flat frequency response or a fast ring-free impulse response. For the optical transmission of microwave and millimeter wave RF signals, such as remote antennas or radar arrays, a flat frequency response is critical. A flat frequency response can be obtained from controlled ringing in the temporal domain. This paper explores the control of ringing in the temporal domain using varied external loads. A fast fall time, ring-free pulse is useful for digital communications applications where ringing can degrade the bit error rate. Fourier transforms show that a ring-free impulse response has a characteristic fall-off at high frequencies. However, this fall-off is detrimental for frequency domain applications, so the optimization condition for the inductance and capacitance is different for these applications. This paper explores the suppression of the impulse response tail by varying the external loads.}, Key = {05299222741} } @article{8249882, Author = {Brown, A.S.}, Title = {Flat, cheap, and under control [electrochemical mechanical planarization]}, Journal = {IEEE Spectr. (USA)}, Volume = {42}, Number = {1}, Pages = {40 - 5}, Year = {2005}, url = {http://dx.doi.org/10.1109/MSPEC.2005.1377874}, Keywords = {chemical mechanical polishing;electrolytic polishing;planarisation;semiconductor device manufacture;}, Abstract = {This paper describes Applied Material's wafer polishing technology, called electrochemical mechanical planarization (ECMP). ECMP is the answer to the problems of electropolishing and chemical mechanical planarization (CMP) of the chip-making process: manufacturing faster, more powerful chips without obliterating their vanishing fine and increasingly fragile features. It is designed to remove excess copper from the top of a newly formed layer of wiring on a chip without damaging the fragile insulation material, called a dielectric, beneath it. ECMP combines aspects of two other technologies, chemical mechanical planarization (CMP) and electropolishing}, Key = {8249882} } @article{04198149916, Author = {Huang, Zhaoran and Cha, Cheolung and Chen, Shuodan and Sarmiento, Tomas and Shen, J.J. and Jokerst, Nan M. and Brooke, Martin A. and May, Gary and Brown, April S.}, Title = {InGaAs MSM Photodetectors Modeling Using DOE Analysis}, Journal = {Proceedings of SPIE - The International Society for Optical Engineering}, Volume = {5178}, Pages = {148 - 155}, Address = {San Diego, CA, United States}, Year = {2004}, url = {http://dx.doi.org/10.1117/12.507337}, Keywords = {Semiconducting indium gallium arsenide;Photolithography;Bandwidth;Field effect transistors;Electric field effects;Optical links;Statistical methods;Optimization;Error analysis;Mathematical models;}, Abstract = {Linear statistical models have been generated to predict the performance of metal-semiconductor-metal (MSM) PDs for multi-gigabit optical interconnections. The models estimate the bandwidth and responsivity of the MSM PDs based on the input factors: absorbing layer thickness, detector size, finger widths and finger gaps. The design of experiments (DOE) approach was employed to obtain the necessary data to construct the models. Numerous samples were fabricated so that multiple devices measurements could serve to both construct and verify the linear statistical models. The MSM PDs were fabricated from material with structure InAlAs/InAlGaAs/InGaAs (2000A, 3000A or 5000A, absorbing layer)/InAlAs. The MSM interdigitated fingers were photolithographically defined with finger gaps and widths varying as DOE parameters. A benzocyclobutene (BCB, Cyclotene 35) layer was spin-coated onto all of the samples as isolation from the probing pads. In the bandwidth analysis, the detector size (S) and material thickness (T) were investigated with a fixed finger width (1 μm) and gap (1 μm). Taking the measured results of these detectors in the design matrix, and using least square regression, the model equations were derived as: Bandwidth (GHz) = 12.87 - 0.065S - 3T - 0.02ST. After these equations were developed, predictive calculated results from these equations were then further used to predict and compare measured results on devices that were not used in the statistical model. This leads to an average deviation between predicted and measured bandwidth of less than 5%. In the responsivity analysis, the predictive calculation leads to an average deviation less than 11%.}, Key = {04198149916} } @article{04348319510, Author = {Seo, Sang-Woo and Cho, Sang-Yeon and Huang, Sa and Brown, April S. and Jokerst, Nan Marie}, Title = {High speed InGaAs thin film MSM photodetector characterization using a fiber-based electro-optic sampling system}, Journal = {Proceedings of SPIE - The International Society for Optical Engineering}, Volume = {5353}, Pages = {48 - 56}, Address = {San Jose, CA, United States}, Year = {2004}, url = {http://dx.doi.org/10.1117/12.531681}, Keywords = {Semiconducting gallium compounds;Thin film devices;Electrooptical devices;Optical fibers;Bandwidth;Microwaves;Photocurrents;Sampling;}, Abstract = {As optoelectronic devices increase in speed, the measurement system used to characterize these devices must have sufficient bandwidth and minimum parasitic loading during test to accurately determine the intrinsic performance of the device under test. Conventional electrical measurement systems have an intrinsic bandwidth due to the available components for test and have parasitic loading due to direct electrical contact to the device under the test. Electro-optic sampling is an excellent measurement technique for characterizing ultra-fast devices because it has high bandwidth, is non-contact, is non-destructive, and relatively non-invasive. In this paper, an optical fiber-based electrooptic sampling system is designed and used for characterizing high speed InGaAs thin film MSM photodetectors. A fiber laser which is operating at λ=1556 nm was used for the sampling and excitation beam. Optical fibers were used to connect each component in the system for flexibility. InGaAs thin film MSM photodetectors were fabricated and characterized. InGaAs thin film MSM photodetectors were bonded onto a coplanar strip line deposited on a benzocyclobutene (BCB)-coated glass substrate for characterization. These thin film photodetectors show high speed operation combined with high responsivity and large detection area compared to P-i-N photodetectors operating at similar speeds.}, Key = {04348319510} } @article{8072961, Author = {Losurdo, M. and Giangregorio, M.M. and Bruno, G. and Brown, A.S. and Doolittle, W.A. and Ptak, A.J. and Myers, T.H.}, Title = {Surface potential measurements of doping and defects in p-GaN}, Journal = {GaN and Related Alloys - 2003 Symposium (Mater. Res. Soc. Symposium Proceedings Vol.798)}, Pages = {805 - 10}, Address = {Boston, MA, USA}, Year = {2004}, Keywords = {beryllium;dielectric function;ellipsometry;Fermi level;gallium compounds;hydrogen;III-V semiconductors;magnesium;passivation;semiconductor epitaxial layers;silicon;surface potential;wide band gap semiconductors;}, Abstract = {The interaction of Be-, Mg-, and Si- doped GaN epitaxial films with atomic hydrogen, produced by a remote r.f. hydrogen plasma, is investigated. The kinetics of the interaction is monitored in real time by spectroscopic ellipsometry through the measurement of the variation of the GaN pseudodielectric function. The passivation effect of hydrogen is inferred by surface potential measurements using scanning Kelvin probe microscopy (SKPM). It is found that the interaction of GaN with hydrogen is a strong function of both the type and level of the doping. Hydrogen treatment is shown to lead to a strong variation of the surface potential and, hence, of the Fermi level position, which is the result of p-dopant passivation by hydrogen. A different interaction of Mg and Be with atomic hydrogen is also observed and monitored in real time by ellipsometry. SKPM is also used for studying the interaction of defects in GaN with atomic hydrogen}, Key = {8072961} } @article{04478466901, Author = {Seo, Sang-Woo and Jokerst, Nan Marie and Cho, Sang-Yeon and Brown, April S. and Huang, Sa and Shin, Jeng Jung and Brooke, Martin A.}, Title = {High-speed large-area inverted InGaAs thin-film metal-semiconductor-metal photodetectors}, Journal = {IEEE Journal on Selected Topics in Quantum Electronics}, Volume = {10}, Number = {4}, Pages = {686 - 693}, Year = {2004}, url = {http://dx.doi.org/10.1109/JSTQE.2004.831677}, Keywords = {Thin films;Semiconducting indium compounds;Electrooptical effects;Electronics packaging;Optical links;Substrates;Sampling;}, Abstract = {Inverted metal-semiconductor-metal (I-MSM) photodetectors, which are thin-film MSMs with the growth substrate removed and fingers on the bottom of the device (to eliminate finger shadowing to enhance responsivity), are reported herein for high-speed high-efficiency large-area photodetectors. Reported herein are the highest speed vertically addressed large-area (40-μm diameter) photodetectors reported to date, which operate with a responsivity of 0.16 A/W and a full-width half-maximum of less than 5 ps. Materials, fabrication processes, heterogeneous integration, and characterization of I-MSM photodetectors are presented in this paper, as measured using a fiber-based electrooptic sampling system. These large-area photodetectors are ideal for vertically addressed high-speed optical links which need alignment-tolerant packaging for cost sensitive applications.}, Key = {04478466901} } @article{04168116486, Author = {Triplett, Gregory E. and Brown, April S. and May, Gary S.}, Title = {Charge modification in InAs/AlxGa1-xSb HEMT structures}, Journal = {Journal of Crystal Growth}, Volume = {265}, Number = {1-2}, Pages = {47 - 52}, Year = {2004}, url = {http://dx.doi.org/10.1016/j.jcrysgro.2004.01.036}, Keywords = {High electron mobility transistors;Semiconductor quantum wells;Doping (additives);Heterojunctions;Epitaxial growth;Interfaces (materials);Fermi level;Carrier concentration;Parameter estimation;Molecular beam epitaxy;}, Abstract = {Intrinsic sheet charge levels in unintentionally doped AlSb/InAs/AlSb quantum wells are reproducibly [similar to] 10<sup>12</sup>/cm<sup>2</sup>. While these levels are suitable for depletion-mode operation, realizing enhancement-mode devices ultimately depends on the ability to significantly reduce sheet charge. In an effort to limit carrier accumulation in the InAs quantum well, we have studied the impact of the addition of a p-type, Be, doping plane between the channel and the cap and the modification of defect densities present in the films. Molecular beam epitaxy (MBE) process conditions including substrate temperature, Be-doping density, and doping plane spacing above the quantum well were varied during growth of InAs-Al<sub>x</sub>Ga<sub>1-x</sub>Sb high electron mobility transistors (HEMTs) structures. Utilizing a 2 <sup>3</sup>-full factorial statistical experimental design plus eight additional runs, the ranges for Be-doping (0-2e12/cm<sup>2</sup>), substrate temperature (350-420°C), and separation above the quantum well (60-80A) were examined. Relationships between MBE process conditions and transport properties in Be-doped InAs-Al<sub>x</sub>Ga<sub>1-x</sub>Sb HEMT structures were established. Among the process parameters investigated, substrate temperature during Be-doping had the most significant impact on 2DEG concentration. Substrate temperature and sheet charge exhibited an inversely proportional relationship, where increasing substrate temperature resulted in decreasing sheet charge values. The lowest charge with corresponding mobility was 6.6×10<sup>10</sup> at 6000cm<sup>2</sup>/V/s. © 2004 Elsevier B.V. All rights reserved.}, Key = {04168116486} } @article{04308280107, Author = {Losurdo, Maria and Giangregorio, Maria M. and Capezzuto, Pio and Bruno, Giovanni and Namkoong, Gon and Doolittle, W. Alan and Brown, April S.}, Title = {Interplay between GaN polarity and surface reactivity towards atomic hydrogen}, Journal = {Journal of Applied Physics}, Volume = {95}, Number = {12}, Pages = {8408 - 8418}, Year = {2004}, url = {http://dx.doi.org/10.1063/1.1745124}, Keywords = {Hydrogen;Molecular beam epitaxy;Sapphire;Thin films;Epitaxial growth;Heterojunctions;Electron diffraction;Electron mobility;Spectroscopic analysis;X ray diffraction;}, Abstract = {The polarity of GaN epitaxial films and its impact on the interaction of GaN surfaces with atomic hydrogen were discussed. GaN epilayers were grown by radio frequency plasma molecular beam epitaxy (MBE) with both GaN and AlN buffer layers. It was found that a different reaction rate exists for N- and Ga-polar GaN with atomic hydrogen, with N-polar GaN exhibiting greater reactivity. The results show that Ga-polar GaN results from the use of AlN buffer layers on sapphire when nitrided.}, Key = {04308280107} } @article{05108871846, Author = {Seo, Sang-Woo and Cha, Cheolung and Cho, Sang-Yeon and Huang, Sa and Jokerst, Nan M. and Brooke, Martin A. and Brown, April S.}, Title = {Etch enhanced low capacitance, large area thin film InGaAs metal-semiconductor-metal photodetectors}, Journal = {Conference Proceedings - Lasers and Electro-Optics Society Annual Meeting-LEOS}, Volume = {1}, Pages = {222 - 223}, Address = {Rio Grande, Puerto Rico}, Year = {2004}, Keywords = {Plasma etching;Capacitance;Semiconducting gallium;Impulse response;Semiconducting indium;Thin films;Adsorption;Photoresistors;Light scattering;Threshold voltage;Metallizing;Diaphragms;Permittivity;}, Abstract = {The enhancement of the impulse response and capacitance performance of thin film InGaAs metal-semiconductor-metal (MSM) was carried out through etching. The capacitances of the MSM were measured using scattering parameter measurements using a lightwave component analyzer. The thin film I-MSM photodetector cladding layers were etched while leaving the adsorbing layers intact. The measured impulse response results show improvement as the thickness of the thin film I-MSMs decrease, which was correlated with the reduction of the capacitance.}, Key = {05108871846} } @article{8066407, Author = {Gon Namkoong and Doolittle, W.A. and Brown, A.S. and Losurdo, M. and Giangregorio, M.M. and Bruno, G.}, Title = {Effect of buffer design on AlGaN/AlN/GaN heterostructures by MBE}, Journal = {GaN and Related Alloys - 2003 Symposium (Mater. Res. Soc. Symposium Proceedings Vol.798)}, Pages = {359 - 64}, Address = {Boston, MA, USA}, Year = {2004}, Keywords = {aluminium compounds;gallium compounds;III-V semiconductors;molecular beam epitaxial growth;semiconductor epitaxial layers;semiconductor growth;semiconductor heterojunctions;surface topography;}, Abstract = {The effect of the buffer layers on the subsequent GaN epitaxial layers and electrical properties of AlGaN/AlN/GaN heterojunction structures nitrided at various temperatures was investigated. For AlN buffer layers, two different growth conditions of AlN buffer layers were introduced to avoid Al droplets. We found that etch pit density and structural quality of GaN epitaxial layer strongly depends on the growth conditions of AlN buffer layers. When using a double buffer layer (low temperature GaN on high temperature AlN) for 200 °C nitridation, the etch pit density was measured to high 10<sup>7</sup> cm<sup>-2</sup> in GaN epitaxial layers. Furthermore, we observed that electrical properties of AlGaN/AlN/GaN heterostructures depend on growth conditions of buffer layers and nitridation temperatures. The mobility in Al<sub>0.33</sub>Ga<sub>0.67</sub>N/AlN/GaN structures grown on single AlN buffer layers for 200 °C nitridation were 1300 cm<sup>2</sup>/Vs at a sheet charge of 1.6 × 10<sup>13</sup> cm<sup>-2</sup>. Using the double buffer layer for 200 °C nitridation, the mobility increased to 1587 cm<sup>2</sup>/Vs with a sheet charge of 1.25 × 10<sup>13</sup> cm<sup>-2</sup>}, Key = {8066407} } @article{04108052618, Author = {Losurdo, Maria and Giuva, Danilo and Bruno, Giovanni and Huang, Sa and Kim, Tong-Ho and Brown, April S.}, Title = {The surface modification and reactivity of LiGaO2 substrates during GaN epitaxy}, Journal = {Journal of Crystal Growth}, Volume = {264}, Number = {1-3}, Pages = {139 - 149}, Year = {2004}, url = {http://dx.doi.org/10.1016/j.jcrysgro.2004.01.018}, Keywords = {Gallium nitride;Molecular beam epitaxy;Nitrides;Reaction kinetics;Nitrogen;Ellipsometry;Hydrogen;Etching;Metallorganic chemical vapor deposition;Vaporization;X ray photoelectron spectroscopy;Atomic force microscopy;Reflection high energy electron diffraction;}, Abstract = {The chemistry and kinetics of lithium gallate (LGO) substrates during nitridation are investigated. Nitridation experiments have been carried out using two remote nitrogen RF plasma sources: in an MBE system and in a remote plasma MOCVD system. The difference between the two nitrogen sources is the pressure. The experiments were run in parallel to demonstrate that the same heterogeneous chemistry applies during LGO nitridation in both MBE and MOCVD environments, provided that the same species is produced in the gas phase. Surface analysis techniques, including X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and spectroscopic ellipsometry (SE), show that an optimal temperature of about 600°C and an optimal time that depends on the incident nitrogen density exists that results in the formation of [similar to] 5A of GaN on LGO. The nitridation process competes with lattice damage that is enhanced by the presence of hydrogen. © 2004 Elsevier B.V. All rights reserved.}, Key = {04108052618} } @article{04368342647, Author = {Losurdo, M. and Giangregorio, M.M. and Capezzuto, P. and Bruno, G. and Namkoong, G. and Doolittle, W.A. and Brown, A.S.}, Title = {Interaction of GaN epitaxial layers with atomic hydrogen}, Journal = {Applied Surface Science}, Volume = {235}, Number = {3}, Pages = {267 - 273}, Address = {Ustron, Poland}, Year = {2004}, url = {http://dx.doi.org/10.1016/j.apsusc.2004.05.152}, Keywords = {Epitaxial growth;Hydrogen;Sapphire;Ion bombardment;Passivation;Thin films;Atomic force microscopy;Ellipsometry;Probes;}, Abstract = {GaN surface passivation processes are still under development and among others hydrogen treatments are investigated. In this study, we use non-destructive optical and electrical probes such as spectroscopic ellipsometry (SE) and surface potential Kelvin probe microscopy (SP-KPM) in conjunction with non-contact atomic force microscopy (AFM) for the study of the different reactivity of Ga-polar and N-polar GaN epitaxial layers with atomic hydrogen. The GaN epitaxial layers are grown by molecular beam epitaxy on sapphire (0001) substrates, and GaN and AlN buffer layers are used to grow N-polar and Ga-polar films, respectively. The atomic hydrogen is produced by a remote rf (13.56MHz) H<sub>2</sub> plasma in order to rule out any ion bombardment of the GaN surface and make the interaction chemical. It is found that the interaction of GaN surfaces with atomic hydrogen depends on polarity, with N-polar GaN exhibiting greater reactivity. Furthermore, it is found that atomic hydrogen is effective in the passivation of grain boundaries and surface defects states. © 2004 Elsevier B.V. All rights reserved.}, Key = {04368342647} } @article{04438417380, Author = {Brown, April S. and Losurdo, Maria and Bruno, Giovanni and Brown, Terence and May, Gary}, Title = {Fundamental reactions controlling anion exchange during the synthesis of Sb/As mixed-anion heterojunctions}, Journal = {Journal of Vacuum Science and Technology B: Microelectronics and Nanometer Structures}, Volume = {22}, Number = {4}, Pages = {2244 - 2249}, Year = {2004}, url = {http://dx.doi.org/10.1116/1.1775201}, Keywords = {Arsenic;Antimony;Reaction kinetics;Heterojunctions;Semiconducting gallium compounds;Dimers;Molecular structure;Molecular beam epitaxy;Synthesis (chemical);Scanning tunneling microscopy;X ray photoelectron spectroscopy;Mathematical models;}, Abstract = {As/Sb and Sb/As anion exchange reactions to control heterojunction interface intermixing in mixed anion structure were investigated. The substrate temperature, anion flux exposure time, and incident anion molecular species were analyzed. The characterization of Sb/AS structures was done by Sb surface segregation and subsequent incorporate in epitaxial overlayers. The result show that As/Sb exchange was significant and enhanced by the use of dimer fluxes.}, Key = {04438417380} } @article{04208160908, Author = {Losurdo, M. and Giuva, D. and Giangregorio, M.M. and Bruno, G. and Brown, A.S.}, Title = {Spectroscopic ellipsometry characterization of interface reactivity in GaAs-based superlattices}, Journal = {Thin Solid Films}, Volume = {455-456}, Pages = {457 - 461}, Address = {Vienna, Austria}, Year = {2004}, url = {http://dx.doi.org/10.1016/j.tsf.2003.11.286}, Keywords = {Superlattices;Ion exchange;Negative ions;Surface treatment;Ternary systems;Microstructure;Ellipsometry;Spectroscopic analysis;Molecular beam epitaxy;}, Abstract = {Pseudodielectric function spectra of GaAs/GaSb<sub>1-y</sub>As<sub>y</sub>, GaSb/GaAs<sub>y</sub>Sb<sub>1-y</sub> and GaAs/GaP<sub>y</sub>As<sub>1-y</sub> superlattices have been measured by spectroscopic ellipsometry in the 0.75-5.5 eV photon energy range. The analysis of the E<sub>1</sub> interband critical point and modeling of spectra has been carried out to investigate the chemistry of the anion exchange reaction and abruptness of interface composition in the superlattices. It has been found that a ternary compound GaP<sub>y</sub>As <sub>1-y</sub> forms in the case of the P-for-As anion exchange reaction. In the case of As-for-Sb anion exchange reaction for (GaSb/GaAs<sub>y</sub>Sb <sub>1-y</sub>)<sub>20</sub> SLs, SE data show that this anion exchange results in the formation not only of a ternary alloy GaAs<sub>y</sub>Sb<sub>1-y</sub>, but also in the formation of isoelectronic compounds AsSb<sub>x</sub> that segregate at the GaSb/GaAs interface. In the case of Sb-for-As anion exchange for (GaAs/GaSbyAs<sub>1-y</sub>)<sub>20</sub> SLs, Sb segregates at the GaAs surface. © 2003 Elsevier B.V. All rights reserved.}, Key = {04208160908} } @article{04278245174, Author = {Losurdo, M. and Giangregorio, M.M. and Bruno, G. and Brown, A.S. and Doolittle, W.A. and Namkoong, Gon and Ptak, A.J. and Myers, T.H.}, Title = {Surface potential measurements of doping and defects in p-GaN}, Journal = {Materials Research Society Symposium - Proceedings}, Volume = {798}, Pages = {805 - 810}, Address = {Boston, MA, United States}, Year = {2003}, Keywords = {Doping (additives);Surface measurement;Kinetic theory;Fermi level;Silicon;Spectroscopy;Ellipsometry;Passivation;Beam plasma interactions;Beryllium;Hydrogen;Magnesium printing plates;}, Abstract = {The interaction of Be-, Mg-, and Si- doped GaN epitaxial films with atomic hydrogen, produced by a remote r.f. hydrogen plasma, is investigated. The kinetics of the interaction is monitored in real time by spectroscopic ellipsometry through the measurement of the variation of the GaN pseudodielectric function. The passivation effect of hydrogen is inferred by surface potential measurements using scanning Kelvin probe microscopy (SKPM). It is found that the interaction of GaN with hydrogen is a strong function of both the type and level of the doping. Hydrogen treatment is shown to lead to a strong variation of the surface potential and, hence, of the Fermi level position, which is the result of p-dopant passivation by hydrogen. A different interaction of Mg and Be with atomic hydrogen is also observed and monitored in real time by ellipsometry. SKPM is also used for studying the interaction of defects in GaN with atomic hydrogen.}, Key = {04278245174} } @article{04498701808, Author = {Seo, S.W. and Shen, J.J. and Jokerst, N.M. and Brown, A.S.}, Title = {Large area, high speed InGaAs thin film MSMs for heterogeneously integrated optoelectronics}, Journal = {OSA Trends in Optics and Photonics Series}, Volume = {88}, Pages = {460 - 463}, Address = {Baltimore, MD, United States}, Year = {2003}, Keywords = {Optoelectronic devices;Thin films;Fiber optics;Electrodes;Indium compounds;Gallium compounds;Diaphragms;Quantum efficiency;Metallizing;Degradation;}, Abstract = {Thin film InGaAs photodetectors for heterogeneously integrated optoelectronics are demonstrated with low dark current (0.16nA at 5V), and high speed (3ps rise time, 6.3ps FWHM), large area (40 μm), and good responsivity (0.19A/W at 5V).}, Key = {04498701808} } @article{03157430661, Author = {Namkoong, Gon and Doolittle, W. Alan and Brown, April S. and Losurdo, Maria and Giangregorio, Maria M. and Bruno, Giovanni}, Title = {The impact of substrate nitridation temperature and buffer design and synthesis on the polarity of GaN epitaxial films}, Journal = {Journal of Crystal Growth}, Volume = {252}, Number = {1-3}, Pages = {159 - 166}, Year = {2003}, url = {http://dx.doi.org/10.1016/S0022-0248(03)00953-9}, Keywords = {Epitaxial growth;Sapphire;Morphology;Annealing;Dislocations (crystals);Substrates;Atomic force microscopy;}, Abstract = {The polarity of GaN epitaxial layers grown on GaN and AlN buffer layers was investigated and found to be dependent on nitridation temperature over the range of 200-700°C. When low temperature (LT), 500°C, GaN buffer layers are used, GaN epitaxial layers grown on 200°C nitrided sapphire have a higher density of N-polar inversion domains. However, a high density of dislocation pits was observed on GaN epitaxial layers based on AFM morphology when GaN epitaxial layers were grown on LT GaN buffer of 700°C nitrided sapphire substrate. With high temperature (HT), 850°C, AlN buffer layers, the density of N-polar inversion domains in GaN epitaxial layers depends on the thickness of AlN buffer layer. The structural quality of Ga-polar GaN epitaxial layer is dramatically improved when LT GaN and HT AlN buffer layers are combined with an optimized annealing time. The measured full-widths at half-maximum of (0002) symmetric and (10.4) asymmetric reflections are 68 and 246 arcsec, respectively, for 1.0 μm GaN epitaxial layers. The results presented here can be implemented to produce low dislocation density, single Ga-polar GaN epitaxial layers. © 2003 Elsevier Science B.V. All rights reserved.}, Key = {03157430661} } @article{7775917, Author = {Kuech, T.F. and Ning Liu and Tong-Ho Kim and Changhyun Yi and Brown, A.S.}, Title = {Alternative substrates for InP and related materials}, Journal = {2003 International Conference Indium Phosphide and Related Materials. Conference Proceedings (Cat. No.03CH37413)}, Pages = {562 -}, Address = {Santa Barbara, CA, USA}, Year = {2003}, url = {http://dx.doi.org/10.1109/ICIPRM.2003.1205442}, Keywords = {gallium arsenide;III-V semiconductors;indium compounds;substrates;wafer bonding;}, Abstract = {We will present examples of wafer bonding as applied to InGaAs/InP system highlighting the effects of the bonding process on the post-bonding device characteristics. Some future directions of alternative substrates for use in InP technologies will be presented}, Key = {7775917} } @article{03447702287, Author = {Doolittle, W. Alan and Namkoong, Gon and Carver, Alexander G. and Brown, April S.}, Title = {Challenges and potential payoff for crystalline oxides in wide bandgap semiconductor technology}, Journal = {Solid-State Electronics}, Volume = {47}, Number = {12}, Pages = {2143 - 2147}, Year = {2003}, url = {http://dx.doi.org/10.1016/S0038-1101(03)00187-4}, Keywords = {Crystals;Oxides;Permittivity;Polarization;}, Abstract = {While growth of wide bandgap semiconductor materials on crystalline oxides (sapphire, lithium gallate, lithium aluminate, zinc oxide and others) has become routine, growth of crystalline oxides on wide bandgap materials remains challenging and minimally explored. The potential payoff in terms of enhanced device performance, increased functionality and reliability warrants examining this option. This presentation aims at targeting key areas, where crystalline oxides could improve wide bandgap semiconductor device performance. Some of these include the use of ferroelectric oxides for power switching applications, oxides with anisotropic dielectric constants for high voltage termination and oxides with large electric flux density near breakdown. Unique polarization engineered structures are described that are enabled by using lithographically defined poled regions in a ferroelectric substrate. The desired crystalline oxide properties, potential implementation challenges and potential pitfalls will be discussed. © 2003 Published by Elsevier Ltd.}, Key = {03447702287} } @article{04288257335, Author = {Losurdo, Maria and Giuva, Danilo and Capezzuto, Pio and Bruno, Giovanni and Brown, Terence and Triplett, Greg and May, Gary and Brown, April S.}, Title = {A study of anion exchange reactions at GaAs surfaces for heterojunction interface control}, Journal = {Materials Research Society Symposium - Proceedings}, Volume = {799}, Pages = {97 - 102}, Address = {Boston, MA, United States}, Year = {2003}, Keywords = {Semiconducting gallium arsenide;Heterojunctions;Superlattices;Diffusion in solids;Energy gap;Negative ions;X ray photoelectron spectroscopy;}, Abstract = {GaP<sub>y</sub>As<sub>1-y</sub>/GaAs, GaAs<sub>y</sub>Sb<sub>i-y</sub>/GaSb and GaSb<sub>y</sub>As<sub>1-y</sub>/GaAs superlattices (SLs) grown by MBE, by exposure of GaAs to phosphorus and antimonide fluxes, and by exposure of GaSb to an arsenic flux, respectively, have been investigated. The focus is on the abruptness of interfaces and understanding the mechanisms associated with anion incorporation and exchange. In the case of the Sb flux interaction with the GaAs surface, the Sb segregation at the GaAs surface inhibits anion exchange. For the case of As over GaSb reactions, anion exchange results in the formation not only of the ternary alloy GaAs<sub>y</sub>Sb<sub>1-y</sub>, but also of isoelectronic compounds AsSb<sub>x</sub> that segregate at the GaSb/GaAs interface. In the case of the P flux interfaction with the GaAs surface, fast in-diffusion of P results in graded GaP<sub>y</sub>As<sub>1-y</sub> layer formation.}, Key = {04288257335} } @article{04278245113, Author = {Namkoong, Gon and Doolittle, W. Alan and Brown, A.S. and Losurdo, M. and Giangregorio, M.M. and Bruno, G.}, Title = {Effect of buffer design on AlGaN/AlN/GaN heterostrucutres by MBE}, Journal = {Materials Research Society Symposium - Proceedings}, Volume = {798}, Pages = {359 - 364}, Address = {Boston, MA, United States}, Year = {2003}, Keywords = {Heterojunctions;Epitaxial growth;Crystal lattices;Organic acids;Desorption;Carrier concentration;X ray diffraction;Reflection high energy electron diffraction;}, Abstract = {The effect of the buffer layers on the subsequent GaN epitaxial layers and electrical properties of AlGaN/AlN/GaN heterojunction structures nitrided at various temperatures was investigated. For AlN buffer layers, two different growth conditions of AlN buffer layers were introduced to avoid Al droplets. We found that etch pit density and structural quality of GaN epitaxial layer strongly depends on the growth conditions of AlN buffer layers. When using a double buffer layer (low temperature GaN on high temperature AlN) for 200 °C nitridation, the etch pit density was measured to high 107 cm<sup>-2</sup> in GaN epitaxial layers. Furthermore, we observed that electrical properties of AlGaN/AlN/GaN heterostructures depend on growth conditions of buffer layers and nitridation temperatures. The mobility in Al<sub>0.33</sub>Ga <sub>0.67</sub>N/AlN/GaN structures grown on single AlN buffer layers for 200 °C nitridation were 1300 cm<sup>2</sup>/Vs at a sheet charge of 1.6×10<sup>13</sup> cm<sup>-2</sup>. Using the double buffer layer for 200 °C nitridation, the mobility increased to 1587 cm<sup>2</sup>/Vs with a sheet charge of 1.25×10<sup>13</sup> cm<sup>-2</sup>.}, Key = {04278245113} } @article{7648070, Author = {Brown, A.S.}, Title = {Superconducting circuit makers pin hopes on wireless filters}, Journal = {IEEE Spectr. (USA)}, Volume = {40}, Number = {4}, Pages = {3 pp. -}, Year = {2003}, Keywords = {superconducting filters;}, Abstract = {The discovery of ceramic superconductors in 1986 sparked dreams of levitating trains, cheap electric power, and desktop medical scanners. Some savvy investors instead set their sights on superconducting microelectronics. In 1987, a group that included Intel cofounder Robert Noyce and Nobel Laureate J. Robert Schrieffer started Superconductor Technologies Inc. (STI). In the same year another group, led by Ethernet pioneer John F. Shoch, started Conductus Inc. Now, 15 years later, the pioneers in superconducting circuits have merged in the hopes of better surviving a market meltdown. By the time the two companies merged with one another, their visions of becoming a foundry for superconducting circuits in general had narrowed to production of superconducting filters to improve cell phone communications}, Key = {7648070} } @article{02176925920, Author = {Yi, Changhyun and Kim, Tong-Ho and Brown, April S.}, Title = {InP-based AlInAs/GaAs0.51Sb0.49/GaInAs single heterojunction bipolar transistor for high-speed and RF wireless applications}, Journal = {Journal of Electronic Materials}, Volume = {31}, Number = {2}, Pages = {95 - 98}, Year = {2002}, Keywords = {Semiconducting aluminum compounds;Semiconducting gallium arsenide;Semiconducting indium gallium arsenide;Heterojunction bipolar transistors;Semiconductor growth;Molecular beam epitaxy;Integrated circuit manufacture;Semiconductor device structures;Application specific integrated circuits;Electric potential;Electric currents;Current density;}, Abstract = {The InP-based AlInAs-GaAsSb-GaInAs heterojunction bipolar transistors (HBTs) have been grown by solid-source molecular-beam epitaxy (SSMBE). Since the AlInAs-GaAsSb heterojunction has a type-II (staggered) band lineup, the conduction-band discontinuity is negligible at 300 K (10 meV). Thus, the turn-on voltage is significantly lower than that of an AlInAs-GaInAs HBT even without compositional grading of the emitter-base junction. A self-aligned process was used to fabricate large area devices. The measured turn-on voltage and collector-emitter offset were 0.36 V and 0.23 V, respectively, with a DC gain of approximately 25 and ideality factors of η<sub>C</sub> = 1.01 and η<sub>B</sub> = 1.1 at J<sub>C</sub> = 10 kA/cm<sup>2</sup> collector-current density.}, Key = {02176925920} } @article{7636394, Author = {Losurdo, M. and Giangregorio, M.M. and Capezzuto, P. and Bruno, G. and Namkoong, G. and Doolittle, W.A. and Brown, A.S.}, Title = {A chemical perspective of GaN polarity: the use of hydrogen plasma dry etching versus NaOH wet etching to determine polarity}, Journal = {Materials and Devices for Optoelectronics and Microphotonics. Symposia (Materials Research Society Symposium Proceedings Vol.722)}, Pages = {103 - 8}, Address = {San Francisco, CA, USA}, Year = {2002}, Keywords = {dislocation density;domains;gallium compounds;III-V semiconductors;semiconductor epitaxial layers;sputter etching;surface morphology;wide band gap semiconductors;}, Abstract = {The use of dry hydrogen plasma etching is evaluated for determination of GaN polarity and critically compared to wet etching in NaOH. It is shown that hydrogen plasma etching is effective in revealing inversion domains (IDs) and some types of dislocations. This is because the surface morphology is unchanged by the hydrogen treatment, and, hence, the surface reactivity is not masked}, Key = {7636394} } @article{02166923808, Author = {Losurdo, M. and Capezzuto, P. and Bruno, G. and Namkoong, G. and Doolittle, W.A. and Brown, A.S.}, Title = {Plasmas for the low-temperature growth of high-quality GaN films by molecular beam epitaxy and remote plasma MOCVD}, Journal = {Physica Status Solidi (A) Applied Research}, Volume = {190}, Number = {1}, Pages = {43 - 51}, Year = {2002}, url = {http://dx.doi.org/10.1002/1521-396X(200203)190:1<43::AID-PSSA43>3.0.CO;2-G}, Keywords = {Gallium nitride;Film growth;Sapphire;Plasmas;Molecular beam epitaxy;Metallorganic chemical vapor deposition;Annealing;Interferometry;Ellipsometry;Electron spectroscopy;Reflection high energy electron diffraction;}, Abstract = {GaN heteroepitaxial growth on sapphire (0001) substrates was carried out by both radio-frequency (rf) remote plasma metalorganic chemical vapor deposition (RP-MOCVD) and molecular beam epitaxy (MBE). A multistep growth process including substrate plasma cleaning and nitridation, buffer growth, its subsequent annealing and epilayer growth was used. In order to achieve a better understanding of the GaN growth, in-situ real time investigation of the surface chemistry is performed for all the steps using the conventional reflection high-energy electron spectroscopy (RHEED) during the MBE process, while laser reflectance interferometry (LRI) and spectroscopic ellipsometry (SE), which do not require UHV conditions, are used for the monitoring of the RP-MOCVD process. The chemistry of the rf N<sub>2</sub> plasma sapphire nitridation and its effect on the epilayer growth and quality are discussed in both MBE and RP-MOCVD.}, Key = {02166923808} } @article{03317575949, Author = {Doolittle, W. Alan and Namkoong, Gon and Carver, Alexander and Henderson, Walter and Jundt, Dieter and Brown, April S.}, Title = {III-nitride growth on lithium niobate: A new substrate material for polarity engineering in III-nitride heteroepitaxy}, Journal = {Materials Research Society Symposium - Proceedings}, Volume = {743}, Pages = {9 - 14}, Address = {Boston, MA, United States}, Year = {2002}, Keywords = {Nitrides;Semiconductor growth;Epitaxial growth;Heterojunctions;Substrates;Crystal lattices;Film growth;Molecular beam epitaxy;Gallium nitride;Aluminum nitride;Nonlinear optics;Optical properties;}, Abstract = {Herein, we discuss the use of a novel new substrate for III-Nitride epitaxy, Lithium Niobate. It is shown that Lithium Niobate (LN) has a smaller lattice mismatch to III-Nitrides than sapphire and can be used to control the polarity of III-Nitride films grown by plasma assisted molecular beam epitaxy. Results from initial growth studies are reported including using various nitridation/buffer conditions along with structural and optical characterization. Comparisons of data obtained from GaN and A1N buffer layers are offered and details of the film adhesion dependence on buffer layer conditions is presented. Lateral polarization heterostructures grown on periodically poled LN are also demonstrated. While work is still required to establish the limits of the methods proposed herein, these initial studies offer the promise for mixing Ill-Nitride semiconductor materials with lithium niobate allowing wide bandgap semiconductors to utilize the acoustic, pyroelectric/ferroelectric, electro-optic, and nonlinear optical properties of this new substrate material as well as the ability to engineer various polarization structures for future devices.}, Key = {03317575949} } @article{02106879531, Author = {Namkoong, Gon and Brown, April S. and Losurdo, Maria and Capezzuto, Pio and Bruno, Giovanni and Alan Doolittle, W.}, Title = {Role of sapphire nitridation temperature on GaN growth by plasma assisted molecular beam epitaxy: Part I. Impact of the nitridation chemistry on material characteristics}, Journal = {Journal of Applied Physics}, Volume = {91}, Number = {4}, Pages = {2499 -}, Year = {2002}, url = {http://dx.doi.org/10.1063/1.1435834}, Key = {02106879531} } @article{02477214629, Author = {Wang, Zhong L. and Brown, April S. and Wang, Y.Q. and Shen, J.J.}, Title = {Engineering vertically aligned InAs/GaAs quantum dot structures via anion exchange}, Journal = {Solid State Communications}, Volume = {122}, Number = {10}, Pages = {553 - 556}, Year = {2002}, url = {http://dx.doi.org/10.1016/S0038-1098(02)00212-0}, Keywords = {Semiconducting gallium arsenide;Negative ions;Self assembly;Crystal growth;Molecular beam epitaxy;Morphology;}, Abstract = {P/As anion exchange is exploited to modify stacked InAs/GaAs quantum dot structures grown by molecular beam epitaxy (MBE). It is shown that the vertical alignment and size uniformity can be remarkably improved via P/As anion exchange. This, therefore, demonstrates a promising approach to tuning the quantum dot morphologies and structures, and hence, the electronic and optoelectronic properties. © 2002 Elsevier Science Ltd. All rights reserved.}, Key = {02477214629} } @article{7402750, Author = {Triplett, G.E. and May, G.S. and Brown, A.S.}, Title = {Using neural networks for RHEED modeling of interfaces in AlGaSb-InAs HEMT devices}, Journal = {2002 GaAs MANTECH Conference. Digest of Papers}, Pages = {157 - 60}, Address = {San Diego, CA, USA}, Year = {2002}, Keywords = {aluminium compounds;gallium compounds;high electron mobility transistors;III-V semiconductors;indium compounds;neural nets;reflection high energy electron diffraction;semiconductor device models;}, Abstract = {In this paper, it is demonstrated that RHEED data obtained during the formation of the interfaces in AlGaSb-InAs HEMT devices can be used to model device important epitaxial layer electrical performance parameters. RHEED intensity oscillations of the specular spot are analyzed using principle component analysis (PCA) and modeled using error backpropagation (BP) neural networks}, Key = {7402750} } @article{02377085936, Author = {Yi, Changhyun and Metzger, Robert A. and Brown, April S.}, Title = {The effect of strained Al0.7In0.3As emitter layers on abrupt N-p+ AlInAs-GaInAs heterojunction diodes and heterojunction bipolar transistors}, Journal = {Journal of Electronic Materials}, Volume = {31}, Number = {8}, Pages = {841 - 847}, Year = {2002}, Keywords = {Semiconducting aluminum compounds;Semiconductor diodes;Heterojunction bipolar transistors;Computer simulation;Electric field effects;Molecular beam epitaxy;Electron transport properties;Carrier concentration;Thermionic emission;Electron tunneling;Electron mobility;Band structure;}, Abstract = {Strained Al<sub>x</sub>In<sub>1-x</sub>As/Ga<sub>0.47</sub>In<sub>0.53</sub>As heterojunction N-p<sup>+</sup> diodes and heterojunction bipolar transistors (HBTs) have been grown on InP substrates by solid-source molecular-beam epitaxy, fabricated, and characterized. To determine the effects of the conduction-band discontinuity at the emitter-base heterojunction on turn-on voltage and ideality factor, a strained Al<sub>0.7</sub>In<sub>0.3</sub>As layer is inserted in the emitter near the base. Changes in transport across the junction are observed as a function of the strained-layer position and thickness. These results were used to implement strained emitter HBTs.}, Key = {02377085936} } @article{02307028319, Author = {Namkoong, Gon and Doolittle, W. Alan and Brown, April S. and Losurdo, Maria and Capezzuto, Pio and Bruno, Giovanni}, Title = {Role of low-temperature (200 °C) nitridation in the growth of GaN by plasma-assisted molecular-beam epitaxy}, Journal = {Journal of Vacuum Science and Technology B: Microelectronics and Nanometer Structures}, Volume = {20}, Number = {3}, Pages = {1221 - 1228}, Address = {Providence, RI}, Year = {2002}, url = {http://dx.doi.org/10.1116/1.1470514}, Keywords = {Gallium nitride;Molecular beam epitaxy;Nitriding;Sapphire;Surface chemistry;Optical properties;Diffusion;Low temperature effects;High temperature effects;Ellipsometry;X ray photoelectron spectroscopy;Secondary ion mass spectrometry;}, Abstract = {The effects of sapphire nitridation temperature on the properties of GaN grown by radiofrequency (rf) plasma assisted molecular-beam epitaxy (MBE) were discussed. It was found that the optical and structural characteristics of GaN epitaxial layers were dramatically improved at a nitridation temperatutre of 200 °C. The analysis showed that the nitridation temperature was a crucial parameter in improvement of the optical and structural quality of GaN epitaxial layers.}, Key = {02307028319} } @article{03467727853, Author = {Kim, Tong-Ho and Yi, Changhyun and Brown, April S. and Moran, Peter and Kuech, Thomas}, Title = {The Heterogeneous Integration of InAlAs/InGaAs Heterojunction Diodes on GaAs: Impact of Wafer Bonding on Structural and Electrical Characteristics}, Journal = {Proceedings IEEE Lester Eastman Conference on High Performance Devices}, Pages = {384 - 392}, Address = {Newark, DE, United States}, Year = {2002}, Keywords = {Semiconducting gallium arsenide;Semiconducting indium gallium arsenide;Current voltage characteristics;X ray diffraction analysis;Secondary ion mass spectrometry;Computer simulation;}, Abstract = {We have investigated the influence of low temperature wafer bonding on the electrical and structural characteristics of InAlAs/InGaAs n-p heterojunction structures with similar structure to an emitter-base junction of InAlAs/InGaAs HBTs. Those n-p junction heterostructures were grown on an InP (100) substrate by solid source MBE. The effect of the wafer bonding process on the structural properties of the epitaxial layers was studied by comparing triple crystal x-ray diffraction measurements and simulations before and after bonding. In addition, the influence of the bonding process on the electrical properties of the heterojunction structures was assessed through SIMS analysis of both the bonded and non-bonded samples and an analysis of the I-V characteristics of diodes fabricated on both the bonded and non-bonded sample. These analyses show that the structural and electrical properties of the as-grown epitaxial layers were negligibly changed by the low temperature wafer transfer process.}, Key = {03467727853} } @article{02216955072, Author = {Seo, Sangwoo and Kang, Sangbeom and Doolittle, William A. and Lee, K.K. and Huang, S. and Jokerst, N.M. and Brown, A.S. and Brooke, M.A.}, Title = {The heterogeneous integration of GaN thin-film metal-semiconductor-metal photodetectors onto silicon}, Journal = {IEEE Photonics Technology Letters}, Volume = {14}, Number = {2}, Pages = {185 - 187}, Year = {2002}, url = {http://dx.doi.org/10.1109/68.980507}, Keywords = {Thin film devices;Gallium nitride;Semiconducting silicon;Silica;Low temperature operations;Etching;Substrates;Lithium compounds;Molecular beam epitaxy;}, Abstract = {The heterogeneous integration of GaN thin-film metal-semiconductor-metal (MSM) photodetectors onto a host substrate of SiO<sub>2</sub>-Si is reported herein. Thin-film GaN photodetectors were separated from the lithium gallate (LiGaO<sub>2</sub>) growth substrate using selective etching, and contact bonded onto an SiO<sub>2</sub>-Si host substrate. The thin-film MSMs exhibited a dark current of 13.36 pA and an UV photoresponse at 308 nm of 0.11 A/W at a reverse bias voltage of 20 V. This first demonstration of GaN thin-film device integration onto SiO<sub>2</sub>-Si using a low-temperature integration process, combined with the advances in GaN material quality on LiGaO<sub>2</sub> substrates, enables the integration of GaN devices with Si circuitry for heterogeneously integrated systems.}, Key = {02216955072} } @article{7160044, Author = {Losurdo, M. and Capezzuto, P. and Bruno, G. and Namkoong, G. and Doolittle, W.A. and Brown, A.S.}, Title = {The chemistry of sapphire nitridation in relation to the GaN structural quality: Why low temperature 200°C nitridation?}, Journal = {Phys. Status Solidi A (Germany)}, Volume = {188}, Number = {2}, Pages = {561 - 5}, Address = {Denver, CO, USA}, Year = {2001}, url = {http://dx.doi.org/10.1002/1521-396X(200112)188:2<561::AID-PSSA561>3.0.CO;2-J}, Keywords = {annealing;chemisorption;gallium compounds;III-V semiconductors;nitridation;photoluminescence;sapphire;semiconductor epitaxial layers;semiconductor growth;substrates;thermally stimulated desorption;wide band gap semiconductors;}, Abstract = {The effect of c-plane sapphire nitridation upon exposure to an rf N<sub>2</sub> plasma at temperatures in the range 100-700°C on the quality of GaN epilayers grown by MBE is investigated. A homogeneous AlN layer is formed at 200°C. Nitridation at higher temperatures creates a rough and non-homogeneous nitridated layer including both AlN and NO. Lowering the nitridation temperature to 200°C results in the improvement of the GaN structural and photoluminescence properties. The results are interpreted in the framework of a chemical model based on the competition between formation of AlN and NO whose adsorption/desorption equilibrium on the sapphire surface strongly depends on temperature}, Key = {7160044} } @article{7160030, Author = {Doolittle, W.A. and Brown, A.S. and Kang, S. and Seo, S.W. and Huang, S. and Jokerst, N.M.}, Title = {Recent advances in III-nitride devices grown on lithium gallate}, Journal = {Phys. Status Solidi A (Germany)}, Volume = {188}, Number = {2}, Pages = {491 - 5}, Address = {Denver, CO, USA}, Year = {2001}, url = {http://dx.doi.org/10.1002/1521-396X(200112)188:2<491::AID-PSSA491>3.0.CO;2-B}, Keywords = {diffusion;dislocation density;electron mobility;field effect transistors;gallium compounds;getters;III-V semiconductors;leakage currents;lithium compounds;photodiodes;semiconductor epitaxial layers;semiconductor growth;substrates;wide band gap semiconductors;}, Abstract = {We discuss recent advances in the growth of III-nitride materials and devices, which include: (i) The reduction of the near-surface threading dislocation density in GaN on lithium gallate (LGO) to ≈2×10<sup>7</sup> cm<sup>-2</sup>. (ii) The demonstration of GaN, 50×130 μm, metal-semiconductor-metal (MSM) photodiodes with extremely low leakage current, 0.11 pA at 2 V and 7.9 pA at 60 V, and UV photoresponse at 308 nm and 20 V of 0.105 A/W. (iii) State of the art MSM devices have been successfully removed from the LGO substrate and attached to silicon wafers with no degradation in current characteristics. (iv) Demonstration of very thin, 0.7 μm HFET structures, grown at a rapid rate of 0.9 μm/h, with near state of the art room temperature 2DEG mobilities of 1365 cm<sup>2</sup>/Vs at a sheet charge of 9×10<sup>12</sup> cm<sup>-2</sup>. (v) The elimination of substrate impurity diffusion by inclusion of gettering buffers has also been demonstrated}, Key = {7160030} } @article{02106878467, Author = {Brown, April S. and Jokerst, Nan Marie and Doolittle, Alan and Brooke, Martin and Kuech, Thomas F. and Seo, Sang-Woo and Kang, Sangbeom and Huang, Sa and Shen, Jeng-Jung}, Title = {Heterogeneous integration: From substrate technology to active packaging}, Journal = {Technical Digest - International Electron Devices Meeting}, Pages = {197 - 200}, Address = {Washington, DC}, Year = {2001}, url = {http://dx.doi.org/10.1109/IEDM.2001.979465}, Keywords = {Semiconducting indium phosphide;Gallium nitride;Semiconducting silicon;Dissimilar materials;Substrates;MIM devices;High electron mobility transistors;Semiconducting indium gallium arsenide;CMOS integrated circuits;Heterojunctions;Molecular beam epitaxy;}, Abstract = {Heterogeneous integration of dissimilar materials and devices is necessary for the continued advancement of electronic and optoelectronic systems. A range of processes has been developed in recent years that will enable system integration and advanced packaging. Herein, we outline our approaches towards heterogeneous integration.}, Key = {02106878467} } @article{01416680007, Author = {Seo, S.W. and Lee, K.K. and Kang, S. and Huang, S. and Doolittle, W.A. and Jokerst, N.M. and Brown, A.S.}, Title = {GaN metal-semiconductor-metal photodetectors grown on lithium gallate substrates by molecular-beam epitaxy}, Journal = {Applied Physics Letters}, Volume = {79}, Number = {9}, Pages = {1372 -}, Year = {2001}, url = {http://dx.doi.org/10.1063/1.1398320}, Key = {01416680007} } @article{01496751276, Author = {Brown, A.S. and Doolittle, W.A. and Jokerst, N.M. and Kang, S. and Huang, S. and Seo, S.W.}, Title = {Heterogeneous materials integration: Compliant substrates to active device and materials packaging}, Journal = {Materials Science and Engineering B: Solid-State Materials for Advanced Technology}, Volume = {87}, Number = {3}, Pages = {317 - 322}, Year = {2001}, url = {http://dx.doi.org/10.1016/S0921-5107(01)00730-9}, Keywords = {Epitaxial growth;Crystal defects;Microelectronics;Substrates;Crystal lattices;}, Abstract = {The drive for the heterogeneous integration of materials has led to significant advances in materials and device processing, and in the understanding of defect production and control during epitaxy. Heterogeneous integration is driven by microelectronic and packaging trends, and the advent of new materials, such as GaN, that do not possess native substrates. During the last decade, these objectives led to research in the development of compliant substrates. While the ideal compliant substrate concept and implementation may be flawed, this research has certainly advanced materials integration technology. This paper will provide an overview of recent results in compliant substrate experiments and interpretation, and the related advancement of materials and device integration and packaging deriving from some of this research. © 2001 Published by Elsevier Science B.V.}, Key = {01496751276} } @article{02427144459, Author = {Shen, Jeng-Jung and Brown, April S. and Wang, Yongqian and Wang, Zhong L.}, Title = {Self-assembled quantum dot transformations via anion exchange}, Journal = {Journal of Vacuum Science and Technology B: Microelectronics and Nanometer Structures}, Volume = {19}, Number = {4}, Pages = {1463 - 1466}, Address = {Tempe, AZ, United States}, Year = {2001}, url = {http://dx.doi.org/10.1116/1.1385916}, Keywords = {Self assembly;Negative ions;Ion exchange;Annealing;Composition;Surface treatment;Nucleation;Temperature;Morphology;}, Abstract = {Anion anneals have different effects on the quantum dot size distributions and vertical self-assembly. Phosphorus anneal at 300°C can enhance the uniformity of the dot size distribution for both 2 and 3 ML multilayer structures. TEM shows vertically aligned dots structure after annealing at 300°C and a relaxed structure after annealing at 350°C. Arsenic anneal increases the dot size, decreases the dots density, and decreases the uniformity of quantum dots distribution.}, Key = {02427144459} } @article{01376641976, Author = {Lee, K.K. and Doolittle, W.A. and Kim, T.-H. and Brown, A.S. and May, G.S. and Stock, S.R. and Zu Rong Dai and Wang, Z.L.}, Title = {A comparative study of surface reconstruction of wurtzite GaN on (0 0 0 1) sapphire by RF plasma-assisted molecular beam epitaxy}, Journal = {Journal of Crystal Growth}, Volume = {231}, Number = {1-2}, Pages = {8 - 16}, Year = {2001}, url = {http://dx.doi.org/10.1016/S0022-0248(01)01307-0}, Keywords = {Gallium nitride;Molecular beam epitaxy;Surface structure;Sapphire;Plasma applications;Reflection high energy electron diffraction;Transmission electron microscopy;Hall effect;Thin films;Semiconducting films;}, Abstract = {We present a comprehensive study of the electrical, optical, and structural properties of wurtzite GaN films grown under various initial growth conditions The GaN films were grown directly on sapphire substrates using GaN nucleation layers by a Riber 3200 system with a radio-frequency plasma source. In situ reflection high-energy electron diffraction (RHEED) reveals a strong correlation between nucleation conditions, including the nitridation step, and the final surface reconstruction of the GaN thin film. Well-defined reconstruction patterns, primarily (2 × 2) and (4 × 4), are observed for some of the nucleation conditions. Hall mobility, photoluminescence (PL), X-ray rocking curve data, and transmission electron microscopy (TEM) measurements are used to interpret the observed relationship. The results show that for the conditions investigated, an unreconstructed (1 × 1) surface after growth correlates with improved electrical, optical, and structural properties. The surface reconstructed thin film exhibits a strong columnar growth with inversion domains (IDs). We attribute the degraded characteristics to the presence of a mixture of both polarities in the films with reconstruction. © 2001 Published by Elsevier Science B.V.}, Key = {01376641976} } @article{01236528551, Author = {Kang, S. and Doolittle, W.A. and Lee, K.K. and Dai, Z.R. and Wang, Z.L. and Stock, S.R. and Brown, A.S.}, Title = {Characterization of AlGaN/GaN structures on various substrates grown by radio frequency-plasma assisted molecular beam epitaxy}, Journal = {Journal of Electronic Materials}, Volume = {30}, Number = {3}, Pages = {156 - 161}, Year = {2001}, Keywords = {Heterojunctions;Semiconducting aluminum compounds;Gallium nitride;Semiconductor growth;Molecular beam epitaxy;Surface properties;Morphology;Atomic force microscopy;Grain size and shape;Surface roughness;Transmission electron microscopy;Interfaces (materials);}, Abstract = {The structural properties and surface morphology of AlGaN/GaN structures grown on LiGaO<sub>2</sub> (LGO), sapphire, and hydride vapor phase epitaxy (HVPE)-grown GaN templates are compared. AlGaN grown on LGO substrates shows the narrowest x-ray full width at half maximum (FWHM) for both symmetric less than or equal 00.4> and asymmetric less than or equal 10.5> reflections. Atomic force microscopy (AFM) analysis on AlGaN surfaces on LGO substrates also show the smoothest morphology as determined by grain size and rms roughness. The small lattice mismatch of LGO to nitrides and easily achievable Ga-polarity of the grown films are the primary reasons for the smoother surface of AlGaN/GaN structure on this alternative substrate. Optimizations of growth conditions and substrate preparation results in step flow growth for an AlGaN/GaN structure with 300 A thick Al<sub>0.25</sub>Ga<sub>0.75</sub>N on 2.4 μm thick GaN. A high III/V flux ratio during growth and recently improved polishing of LGO substrates aids in promoting two dimensional step flow growth. The GaN nucleation layer directly on the LGO substrates showed no evidence of mixed phase cubic and hexagonal structure that is typically observed in the nucleation buffer on sapphire substrates. Cross-sectional high-resolution transmission electron microscopy (HRTEM) was performed on an AlGaN/GaN hetero-structure grown on LGO. The atomic arrangement at the AlGaN/GaN interface was sharp and regular, with locally observed monolayer and bilayer steps.}, Key = {01236528551} } @article{01045602795, Author = {Namkoong, Gon and Doolittle, W. Alan and Brown, April S.}, Title = {Incorporation of Mg in GaN grown by plasma-assisted molecular beam epitaxy}, Journal = {Applied Physics Letters}, Volume = {77}, Number = {26}, Pages = {4386 -}, Year = {2000}, url = {http://dx.doi.org/10.1063/1.1334942}, Key = {01045602795} } @article{00085279621, Author = {Jokerst, Nan Marie and Brooke, Martin A. and Laskar, Joy and Wills, D. Scott and Brown, April S. and Ingram, Mary Ann}, Title = {Building collaborative teams for multi-disciplinary educational projects in optoelectronics}, Journal = {Proceedings of SPIE - The International Society for Optical Engineering}, Volume = {3831}, Pages = {25 - 35}, Address = {Cancun, Mexico}, Year = {2000}, url = {http://dx.doi.org/10.1117/12.388713}, Keywords = {Engineering education;Strategic planning;}, Abstract = {Multidisciplinary team-oriented research is an effective method for investigating systems spanning multiple knowledge areas. Building on cross-functional team strategies developed for highly competitive industries, experts from a variety of technical domains can be brought together in a team and focused toward a common set of goals. However, building and maintaining these teams is an art that combines technical, social, and management skills, and requires proactive, conscious attention to enable and achieve positive results. This paper explores some avenues toward effective multi-disciplinary team building, and explores the educational potential associated with team-oriented research. The first step in team research is to identify an appropriate technical topic and to build a team around the technical areas associated with that topic. Consensus building is a key aspect to successful team research, as is the goal that every team member achieves research sub-goals as part of the larger effort. Team researchers optimally have a willingness to act in a cooperative rather than competitive fashion with team members, initially communicate with minimal jargon, meet regularly with other team members, share resources, and be personally responsible for their portions of the project. Additional strategies include recognizing and appreciating myriad levels of diversity in the group, valuing the cross disciplinary education of team members, inserting new technology when appropriately mature, and setting timelines and resource allocation using a consensus approach. Multi-disciplinary teams can address problems which are higher in complexity than those addressed by individuals, yet also offer the leveraging, and time and funding buffering that is so important in shortening research time cycles.}, Key = {00085279621} } @article{01045593375, Author = {Jokerst, Nan M. and Brooke, Martin A. and Laskar, J. and Wills, D. Scott and Brown, A.S. and Vrazel, M. and Jung, S. and Joo, Y. and Chang, J.J.}, Title = {Microsystem optoelectronic integration for mixed multisignal systems}, Journal = {IEEE Journal on Selected Topics in Quantum Electronics}, Volume = {6}, Number = {6}, Pages = {1231 - 1239}, Year = {2000}, url = {http://dx.doi.org/10.1109/2944.902172}, Keywords = {VLSI circuits;CMOS integrated circuits;Semiconducting gallium compounds;Semiconducting silicon;Optical interconnects;MESFET devices;Computer networks;}, Abstract = {The integration and packaging of optoelectronic devices with electronic circuits and systems has growing application in many fields, ranging from long to micro haul links. An exploration of the opportunities, integration technologies, and some recent results using thin-film device heterogeneous integration with Si CMOS VLSI and GaAs MESFET circuit technologies are presented in this paper. Applications explored herein include alignment tolerant optoelectronic links for network interconnections, smart pixel focal plane array processing through the integration of imaging arrays with sigma delta analog to digital converters underneath each pixel, and three-dimensional computational systems using vertical through-Si optical interconnections.}, Key = {01045593375} } @article{00085291395, Author = {Lee, Kyeong K. and Doolittle, William A. and Brown, April S. and May, Gary S. and Stock, Stuart R.}, Title = {Using statistical experimental design to investigate the role of the initial growth conditions on GaN epitaxial films grown by molecular beam epitaxy}, Journal = {Journal of Vacuum Science and Technology B: Microelectronics and Nanometer Structures}, Volume = {18}, Number = {3}, Pages = {1448 - 1452}, Year = {2000}, url = {http://dx.doi.org/10.1116/1.591401}, Keywords = {Semiconducting gallium compounds;Film growth;Nucleation;Crystal orientation;Substrates;Molecular beam epitaxy;Statistical methods;Nitrogen;Hall effect;Carrier mobility;Atomic force microscopy;Reflection high energy electron diffraction;}, Abstract = {The initial growth stage of GaN growth directly on basal plane sapphire substrate is investigated. Statistical experimental design is used for the optimization of processes with a large number of interwoven effects. The effects of growth conditions on electrical and surface morphology are analyzed by means of Hall mobility and atomic force microscopy. The interactions between Ga flux and nitrogen power during the buffer growth are discussed.}, Key = {00085291395} } @article{00075228398, Author = {Kang, Sangbeom and Doolittle, W. Alan and Stock, Stuart R. and Brown, April S.}, Title = {Comparison of AlGaN and GaN grown on various substrates: Step flow growth on LiGaO2 at low growth temperature}, Journal = {Materials Science Forum}, Volume = {338 (II}, Pages = {1499 - 1502}, Address = {Research Triangle Park, NC, USA}, Year = {2000}, Keywords = {Heterojunctions;Semiconducting aluminum compounds;Semiconducting gallium compounds;Vapor phase epitaxy;Semiconductor growth;Lithium compounds;Sapphire;Morphology;Dislocations (crystals);Crystal symmetry;Crystal lattices;Nitrides;}, Abstract = {AlGaN/GaN heterostructures were grown on LiGaO<sub>2</sub> (LGO), sapphire, and hydride vapor phase epitaxy (HVPE) grown GaN substrates. Structural properties and surface morphology of each film was compared. LGO substrates produced the lowest FWHM values for both symmetric [Left Angle Bracket] 00.4 [Right Angle Bracket] and asymmetric [Left Angle Bracket] 10.5 [Right Angle Bracket] reflections. The films grown on LGO substrate also showed the best morphology. The small lattice mismatch of LGO to nitrides and Ga-polarity of grown films could be the primary reason for the smoother surface of AlGaN/GaN structure on LGO substrates. In developing the HFET structure on the LGO substrate, we have observed step flow growth in a structure with 300 angstroms thick Al<sub>0.25</sub>Ga<sub>0.75</sub>N on 2.4 µm thick GaN, which is very similar to the films grown by MOCVD. A high III/V flux ratio during growth and recently improved polishing of LGO substrates may have aided in promoting two dimensional step flow growth.}, Key = {00075228398} } @article{00045142146, Author = {Kim, Tong-Ho and Brown, April S. and Metzger, Robert A.}, Title = {Electrical properties of InAlAs/InAsxP1-x/InP composite-channel modulation-doped structures grown by solid source molecular beam epitaxy}, Journal = {Journal of Electronic Materials}, Volume = {29}, Number = {2}, Pages = {215 - 221}, Year = {2000}, Keywords = {Semiconducting indium phosphide;Semiconductor doping;Molecular beam epitaxy;X ray diffraction analysis;Semiconductor quantum wells;Carrier mobility;Surface roughness;}, Abstract = {We report on the electrical characteristics of the two-dimensional electron gas (2DEG) formed in an InAlAs/InAs<sub>x</sub>P<sub>1-x</sub>/InP pseudomorphic composite-channel modulation-doped (MD) structure grown by solid source (arsenic and phosphorus) molecular beam epitaxy (SSMBE). The As composition, x, of strained InAs<sub>x</sub>P<sub>1-x</sub> was determined by x-ray diffraction analysis of InP/InAs<sub>x</sub>P<sub>1-x</sub>/InP multi-quantum wells (MQWs) with compositions of x = 0.14 to x = 0.72. As the As composition increases, the room temperature sheet resistance of InAlAs/InAs<sub>x</sub>P<sub>1-x</sub>/InP composite-channel MD structures grown over a range of As compositions decreased from 510 to 250 Ω/cm<sup>2</sup>, resulting from the greater 2DEG confinement and lower electron effective mass in the InAs<sub>x</sub>P<sub>1-x</sub> channel as x increases. The influence of growth conditions and epitaxial layer designs on the 2DEG mobility and concentration were investigated using 300 K and 77 K Hall measurements. As the exposure time of the As<sub>4</sub> flux on the growth front of InAs<sub>x</sub>P<sub>1-x</sub> increased during growth interruptions, the 2DEG mobility, in particular the 77 K mobility, was considerably degraded due to increased roughness at the InAlAs/InAs<sub>x</sub>P<sub>1-x</sub> interface. For the InAlAs/InAs<sub>0.6</sub>P<sub>0.4</sub>/InP composite-channel MD structure with a spacer thickness of 8 nm, the room temperature 2DEG mobility and density were 7200 cm<sup>2</sup>/Vs and 2.5×10<sup>12</sup> cm<sup>-2</sup>, respectively. These results show the great potential of the InAlAs/InAs<sub>x</sub>P<sub>1-x</sub>/InP pseudomorphic composite-channel MD heterostructure for high frequency, power device applications.}, Key = {00045142146} } @article{6869462, Author = {Gon Namkoong and Doolittle, W.A. and Sangbeom Kang and Huang Sa and Brown, A.S. and Stock, S.R.}, Title = {Low temperature nitridation combined with high temperature buffer annealing for high quality GaN grown by plasma-assisted MBE}, Journal = {MRS Internet J. Nitride Semicond. Res. (USA)}, Volume = {5S1}, Year = {2000}, Keywords = {annealing;gallium compounds;grain size;III-V semiconductors;molecular beam epitaxial growth;nitridation;plasma deposition;wide band gap semiconductors;}, Abstract = {The effect of the initial nitridation of the sapphire substrate on the GaN crystal quality as a function of substrate temperature was studied. GaN layers were grown by plasma-assisted molecular beam epitaxy (MBE) on sapphire substrates nitridated at different substrate temperatures. A strong improvement in the GaN crystal quality was observed at 100°C nitridation temperature. Symmetric (0004) and asymmetric (10-5) full widths at half maximum (FWHM) of the X-ray rocking curves were 136 and 261 arcsec, respectively. This compares to an X-ray rocking curve full width at half maximum of 818 arcsec (0004) for conventional MBE buffer conditions. For our conventional buffer conditions, sapphire substrates were exposed to a N plasma at temperatures above 500°C for 10 min and then 25-50 nm buffers were deposited without annealing at high temperature. The low temperature nitridation also shows an enhancement of the lateral growth of the GaN, resulting in larger grain sizes. The largest grain size achieved was approximately 2.8 μm, while the average grain size was approximately 2.4 μm at 100°C nitridation temperature}, Key = {6869462} } @article{00115391371, Author = {Brown, April S. and Doolittle, W. Alan}, Title = {Status and promise of compliant substrate technology}, Journal = {Applied Surface Science}, Volume = {166}, Number = {1}, Pages = {392 - 398}, Year = {2000}, url = {http://dx.doi.org/10.1016/S0169-4332(00)00455-4}, Keywords = {Semiconducting glass;Semiconducting gallium compounds;Semiconductor growth;Chemical bonds;}, Abstract = {Compliant substrates offer significant promise as a new approach for strain management in semiconductors. The primary application is to produce device-quality highly mismatched materials on dissimilar substrates. Various implementations and processes for achieving substrate compliancy have been proposed and demonstrated. These include the use of twist-, glass-, and metal-bonds, and the use of engineered templates realized with laterally oxidized Al-containing alloys. A recent focus in our work has been on the growth of GaN on a novel and easily removable substrate - lithium gallate - for regrowth on a bonded GaN template.}, Key = {00115391371} } @article{00085299636, Author = {Brown, April S. and Doolittle, W. Alan and Kang, Sangbeom and Shen, Jeng-Jung and Wang, Z.L. and Dai, Z.}, Title = {Growth of GaN on lithium gallate (LiGaO2) substrates for material integration}, Journal = {Journal of Electronic Materials}, Volume = {29}, Number = {7}, Pages = {894 - 896}, Address = {Lake Buena Vista, FL, USA}, Year = {2000}, Keywords = {Semiconductor growth;Lithium compounds;Substrates;Strain;Bonding;Thermal stress;Relaxation processes;Dissimilar materials;Crystal lattices;}, Abstract = {Compliant substrates offer a new approach for strain management in semiconductors. Various implementations and processes for achieving substrate compliancy have been proposed and demonstrated. These include the use of twist-, glass-, and metal-bonds. A recent focus in our work has been on the growth of GaN on a novel and easily removable substrate-lithium gallate-for the ultimate regrowth on a bonded GaN template. The bonding technology is important to reduce thermal stresses during the regrowth step. Herein, we focus on the understanding of the growth of GaN on lithium gallate.}, Key = {00085299636} } @article{6986282, Author = {Jokerst, N. and Brooke, M.A. and Laskar, J. and Wills, D. and Brown, A.S. and Vendier, O. and Bond, S.W. and Cross, J.B. and Vrazel, M. and Thomas, M. and Lee, M. and Jung, S. and Joo, Y. and Chang, J.J.}, Title = {Smart photonics: optoelectronics integrated with Si CMOS VLSI circuits}, Journal = {Proc. SPIE - Int. Soc. Opt. Eng. (USA)}, Volume = {4109}, Pages = {241 - 51}, Address = {San Diego, CA, USA}, Year = {2000}, Keywords = {integrated logic circuits;integrated optics;integrated optoelectronics;optoelectronic devices;}, Abstract = {Smart photonics, the integration of optoelectronic devices with electronic circuits and systems, has growing applications in many fields, one of which is computing. An exploration of the opportunities, integration technologies, and some recent results using thin film optoelectronic and electronic device integration with Si CMOS VLSI and GaAs MESFET technologies are presented herein. Applications explored herein include low cost alignment tolerant optoelectronic interconnection links for network interconnections, smart focal plane array processing through the integration of imaging arrays with sigma delta analog to digital converters underneath each pixel, and three dimensional computational systems using vertical through-Si optical interconnections}, Key = {6986282} } @article{01506759453, Author = {Shen, J.-J. and Kim, T.-H. and Brown, A.S.}, Title = {Growth and characterization of InGaAs/AlInAs HEMT structures on oxide-bonded InGaAs substrates}, Journal = {IEEE International Symposium on Compound Semiconductors, Proceedings}, Pages = {131 - 135}, Address = {Monterey, CA}, Year = {2000}, url = {http://dx.doi.org/10.1109/ISCS.2000.947142}, Keywords = {High electron mobility transistors;Semiconducting indium gallium arsenide;Electric properties;Electron mobility;Morphology;Lattice constants;X ray analysis;}, Abstract = {InGaAs/AlInAs HEMT structures have been grown on oxide-bonded InGaAs substrates. De-oxidation and growth conditions are developed that enable good electrical properties. The highest electron mobility obtained was 7258 cm<sup>2</sup>/V at 300K. The surface morphology showed undulations. X-ray rocking curve analysis shows differences in lattice constants between the samples grown on control substrates and the oxide-bonded substrates.}, Key = {01506759453} } @article{99094798346, Author = {Matyi, R.J. and Doolittle, W.A. and Brown, A.S.}, Title = {High resolution X-ray diffraction analyses of GaN/LiGaO2}, Journal = {Journal of Physics D: Applied Physics}, Volume = {32}, Number = {10A}, Pages = {61-64 -}, Address = {Durham, UK}, Year = {1999}, url = {http://dx.doi.org/10.1088/0022-3727/32/10A/313}, Keywords = {Semiconducting gallium compounds;Lithium compounds;Molecular beam epitaxy;Epitaxial growth;Crystal structure;Temperature;}, Abstract = {Lithium gallate (LiGaO<sub>2</sub>) is gaining increasing attention as a potential substrate for the growth of the important semiconductor GaN. In order to better understand this material we have performed high-resolution double- and triple-axis x-ray diffraction analyses of both the starting LiGaO<sub>2</sub> and GaN/LiGaO<sub>2</sub> following epitaxial growth. A high-resolution triple-axis reciprocal space map of the substrate showed a sharp, well-defined crystal truncation rod and a symmetric streak of intensity perpendicular to q<sub>002</sub>, suggesting high structural quality with mosaic spread. Triple-axis scans following GaN growth showed (1) the development of isotropic diffuse scatter around the LiGaO<sub>2</sub> (002) reflection, (2) the presence of a semi-continuous intensity streak between the LiGaO<sub>2</sub> (002) and GaN (0002) reflections, and (3) a compact pattern of diffuse scatter around the GaN (0002) reflection that becomes increasingly anisotropic as the growth temperature is increased. These results suggest that LiGaO<sub>2</sub> permits the epitaxial growth of GaN with structural quality that may be superior to that observed when growth is performed on SiC or Al<sub>2</sub>O<sub>3</sub>.}, Key = {99094798346} } @article{99104871880, Author = {Kim, T.-H. and Brown, A.S. and Metzger, R.A.}, Title = {Optical and structural properties of strained InAlAs/InAsxP1-x multi-quantum wells grown by solid source molecular beam epitaxy}, Journal = {Journal of Applied Physics}, Volume = {86}, Number = {5}, Pages = {2622 - 2627}, Year = {1999}, url = {http://dx.doi.org/10.1063/1.371101}, Keywords = {Heterojunctions;Semiconducting indium phosphide;Photoluminescence;Molecular beam epitaxy;Strain;X ray crystallography;Semiconductor growth;}, Abstract = {The growth of InP/InAs<sub>x</sub>P<sub>1-x</sub> and InAlAs/InAs<sub>x</sub>P<sub>1-x</sub> heterostructures was studied using P and As sources. The As<sub>4</sub> flux is incorporated much less efficiently into higher As percentage InAsP due to the higher strain in the grown InAsP film. The InP/InAsP multiple quantum wells showed photoluminescence at full width at half maximums of 12-19 meV at 4.2 K.}, Key = {99104871880} } @article{99124946441, Author = {Dagnall, G. and Brown, A.S. and Stock, S.R.}, Title = {Arsenic incorporation in InAsP/InP quantum wells}, Journal = {Journal of Electronic Materials}, Volume = {28}, Number = {10}, Pages = {1108 - 1110}, Year = {1999}, Keywords = {Semiconducting indium phosphide;Arsenic;Molecular beam epitaxy;Semiconductor growth;}, Abstract = {InAsP/InP multiquantum well structures were grown by solid source molecular beam epitaxy using either As<sub>2</sub> or As<sub>4</sub> over a substrate temperature range of 420-535 °C. All quantum wells had similar arsenic compositions with a 2.2% standard deviation regardless of arsenic species or growth temperature. This temperature insensitivity of arsenic incorporation in InAsP is in sharp contrast to InGaAsP in which arsenic composition is very sensitive to both substrate temperature and gallium percentage in the compound. The insensitivity of arsenic incorporation in InAsP to substrate temperature may result from growth in a phosphorus rich condition with indium as the only available cation.}, Key = {99124946441} } @article{99124935595, Author = {Dagnall, Georgiana and Shen, Jeng-Jung and Kim, Tong-Ho and Metzger, Robert A. and Brown, April S. and Stock, Stuart R.}, Title = {Solid source MBE growth of InAsP/InP quantum wells}, Journal = {Journal of Electronic Materials}, Volume = {28}, Number = {8}, Pages = {933 - 938}, Year = {1999}, Keywords = {Semiconducting indium compounds;Molecular beam epitaxy;Substrates;Crystal structure;Dimers;Temperature;X ray diffraction analysis;Arsenic;Photoluminescence;Surface roughness;Atomic force microscopy;}, Abstract = {Strained InAsP multiquantum wells (MWQs) were grown on InP(100) substrates by solid source molecular beam epitaxy and were characterized to relate structural and optical quality to growth conditions. The multiquantum wells were grown using either dimer or tetramer arsenic (As<sub>2</sub> or As<sub>4</sub>) over the substrate temperature range of 420-535°C. θ-2θ x-ray diffraction measurements showed only slight differences between arsenic compositions in the quantum wells grown with As<sub>2</sub> or As<sub>4</sub>. 300K and 8K photoluminescence full width at half max (FWHM) decreased at higher growth temperatures regardless of the arsenic species used. The 8K photoluminescence FWHM and the surface roughness measured by atomic force microscopy are found to be less sensitive to substrate growth temperature for the multiquantum wells growth with As<sub>2</sub> as opposed to As<sub>4</sub>.}, Key = {99124935595} } @article{00024997668, Author = {Doolittle, W.A. and Brown, A.S.}, Title = {Compliant substrate processes}, Journal = {Materials Research Society Symposium - Proceedings}, Volume = {570}, Pages = {225 - 234}, Address = {San Frnacisco, CA, USA}, Year = {1999}, Keywords = {Substrates;Dissimilar materials;Semiconductor growth;Band structure;Strain rate;Semiconductor device manufacture;Epitaxial growth;Crystal defects;Thermal expansion;Transmission electron microscopy;X ray diffraction analysis;}, Abstract = {Recent results indicate that compliant substrates offer significant promise as a new approach for strain management in semiconductors. The potential applications include 1) the growth of device-quality highly mismatched materials on dissimilar substrates, and 2) the lateral control of material properties resulting from the effects of strain on bandstructure and/or growth dynamics. A significant amount of research in this area is dedicated to the reduction of extrinsic processing effects resulting from compliant substrate fabrication, and the development of simple models for understanding the observed reduction in defect density and/or strain in the epitaxial films grown on compliant substrates. A recent focus in our work has been on the growth of GaN on a novel and easily removable substrate - lithium gallate- for the regrowth on a bonded GaN template. The first step in this approach is the optimization of the growth of GaN on lithium gallate. In addition, this approach requires the use of an appropriate bonding layer to reduce the strain or defect production during growth due to coefficient of thermal expansion mismatches between the GaN sample and the handle wafer. Our work in this area will be highlighted in the context of an overview of various compliant substrate approaches and current results that indicate their efficacy.}, Key = {00024997668} } @article{99084751765, Author = {Dagnall, G. and Stock, S.R. and Brown, A.S.}, Title = {Growth of InAsP/InP quantum wells by solid source MBE on misoriented and exact InP (1 1 1)B: Substrate temperature and arsenic species effects}, Journal = {Journal of Crystal Growth}, Volume = {201-202}, Pages = {242 - 247}, Address = {Cannes}, Year = {1999}, url = {http://dx.doi.org/10.1016/S0022-0248(98)01330-X}, Keywords = {Semiconductor quantum wells;Semiconducting indium phosphide;Molecular beam epitaxy;Substrates;Crystal orientation;X ray diffraction analysis;Atomic force microscopy;Photoluminescence;}, Abstract = {Two series of strained InAsP/InP multiquantum wells (MQWs) were grown by solid source molecular beam epitaxy (SSMBE) simultaneously on Fe-doped InP substrates with a growth orientation of either (1 0 0), exact (1 1 1)B, and (1 1 1)B misoriented 1° toward [Left Angle Bracket] -2 1 1 [Right Angle Bracket] . The MQWs were grown using either dimer or tetramer arsenic (As<sub>2</sub> or As<sub>4</sub>) over a substrate temperature range of 420-535 °C. The θ-2θ X-ray diffraction measurements, the atomic force microscopy (AFM) images of the surfaces, and the 8 K photoluminescence (PL) full-width at half-maximum (FWHM) values of the (1 1 1)B samples showed general improvement in the samples' material properties with increasing substrate temperature. While the X-ray diffraction measurements and the AFM images showed little difference between As<sub>2</sub> and As<sub>4</sub>, the 8 K PL FWHM values varied greatly with respect to the arsenic species used. The exact (1 1 1)B samples had narrower 8 K PL FWHM values when grown with As<sub>2</sub>. For growth on misoriented (1 1 1)B InP, the 8 K FWHM values narrowed with As<sub>4</sub>. The misoriented (1 1 1)B samples had the narrowest 8 K PL FWHM when grown with As<sub>4</sub> at a temperature of 520 °C; the exact (1 1 1)B at 495 °C when grown with As<sub>2</sub>.}, Key = {99084751765} } @article{04057901360, Author = {Kang, Sangbeom and Doolittle, William A. and Brown, April S. and Stock, Stuart R.}, Title = {Electrical and structural characterization of AlxGa1-xN/GaN heterostructures grown on LiGaO2 substrates}, Journal = {Applied Physics Letters}, Volume = {74}, Number = {22}, Pages = {3380 - 3382}, Year = {1999}, url = {http://dx.doi.org/10.1063/1.123351}, Abstract = {In this letter, we report on the properties of a Al<sub>x</sub>Ga<sup>1-x</sup>N/GaN heterostructure grown on LiGaO<sub>2</sub>. A two-dimensional electron gas (2DEG) is observed with mobility of 731 cm<sup>2</sup>/V s at room temperature and 2166 cm<sup>2</sup>/V s at 77 K. A comparison of the structural quality of the heterostructure as determined by x-ray diffraction shows significant improvement in comparison to a similar structure grown on a sapphire substrate. Secondary ion mass spectroscopy analysis indicates that lithium diffuses into the GaN during growth. The concentration decreases by two orders of magnitude from the substrate to the surface in a 0.8 μm thick GaN film. The enhancement of the mobility of the 2DEG compared to that of electrons in a uniformly doped film is due, in part, to the proximity of the 2DEG to the film surface, where the Li concentration is lower. In addition, we believe that the surface roughness plays a role in the mobility of the 2DEG. Despite these extrinsic factors, the good conductivity of the 2DEG shows the promise of LiGaO<sub>2</sub> as a substrate for device-quality GaN. © 1999 American Institute of Physics.}, Key = {04057901360} } @article{00025003964, Author = {Jokerst, Nan Marie and Brooke, Martin A. and Laskar, Joy and Wills, D. Scott and Brown, April S. and Vendier, Olivier and Bond, Steven and Cross, Jeffrey and Vrazel, Michael and Thomas, Mikkel and Lee, Myunghee and Jung, Sungyung and Joo, Yoong Joon and Chang, Jae Joon}, Title = {Smart photonics: Optoelectronics integrated onto Si CMOS circuits}, Journal = {Conference Proceedings - Lasers and Electro-Optics Society Annual Meeting-LEOS}, Volume = {2}, Pages = {423 - 424}, Address = {San Francisco, CA, USA}, Year = {1999}, url = {http://dx.doi.org/10.1109/LEOS.1999.811779}, Keywords = {Silicon wafers;Thin film circuits;CMOS integrated circuits;VLSI circuits;Optical links;Optical interconnects;Electronics packaging;}, Abstract = {Smart photonics, or the integration of optoelectronic (OE) devices and links with circuitry such as Si complementary metal oxide semiconductor (CMOS) very large scale integrated (VLSI) circuits, can yield both advanced optical links and possibly integrated solutions for optoelectronic interfaces and interconnections to standard electronic systems. Coupled with alignment tolerant designs, these implementations may yield cost effective solutions which are compatible and integrable with electronic systems. The options in stacking of thin films circuit or in the vertical optical interconnection of Si CMOS circuits using through-Si optical signals are explored in the context of hybrid thin film integration and packaging.}, Key = {00025003964} } @article{98054210657, Author = {Kropewnicki, Thomas J. and Doolittle, W. Alan and Carter-Coman, Carrie and Kang, Sangboem and Kohl, Paul A. and Jokerst, Nan Marie and Brown, April S.}, Title = {Selective wet etching of lithium gallate}, Journal = {Journal of the Electrochemical Society}, Volume = {145}, Number = {5}, Pages = {88-90 -}, Year = {1998}, Keywords = {Etching;Crystal lattices;Semiconductor growth;Substrates;Thin films;Film growth;Semiconducting films;}, Abstract = {Lithium gallate (LGO) is an attractive, near lattice matched substrate for the growth of GaN. In addition, LGO substrates provide a convenient route to forming thin films of GaN as used in substrate removal or lift-off processes. We report the wet etching of LGO substrates for the production of GaN thin films. Two face-selective LGO etches have been used for the processing of substrates. The etch rate of the cation face is reported here for the first time and is 0.25 μm min<sup>-1</sup> at 50 °C. The etching solution is safe and benign to most materials including metallic bonding.}, Key = {98054210657} } @article{99024581247, Author = {Shen, Jeng-Jung and Jokerst, Nan Marie and Brown, April S.}, Title = {Compliant substrate strain modulated epitaxy for WDM laser arrays}, Journal = {Conference Proceedings - Lasers and Electro-Optics Society Annual Meeting-LEOS}, Volume = {1}, Pages = {95 - 96}, Address = {Orlando, FL, USA}, Year = {1998}, Keywords = {Wavelength division multiplexing;Epitaxial growth;Mathematical models;Substrates;Energy gap;Strain;Semiconductor device manufacture;}, Abstract = {A new method for making a multiple-wavelength laser array by using strain modulated epitaxy is described. This growth process, which enables growth on a smooth substrate surface while enabling three dimensional band structure engineering, uses a bottom-patterned compliant substrate to modulate the strain variation on the epitaxial layer grown on the compliant substrate. To achieve the strain variation as a function of lateral position on the grown sample, a bottom patterned compliant substrate is used to vary the strain. A mathematical model has been developed for the realization of a multiple wavelength laser array using bottom patterned compliant substrates.}, Key = {99024581247} } @article{98094378442, Author = {Brown, April S.}, Title = {Compliant substrate technology: status and prospects}, Journal = {Journal of Vacuum Science & Technology B: Microelectronics Processing and Phenomena}, Volume = {16}, Number = {4}, Pages = {2308 -}, Year = {1998}, url = {http://dx.doi.org/10.1116/1.590166}, Key = {98094378442} } @article{98074283107, Author = {Shen, Jeng-Jung and Brown, April S. and Metzger, Robert A. and Sievers, Barry and Bottomley, Lawrence and Eckert, Patrick and Carter, W. Brent}, Title = {Modification of quantum dot properties via surface exchange and annealing: substrate temperature effects}, Journal = {Journal of Vacuum Science & Technology B: Microelectronics Processing and Phenomena}, Volume = {16}, Number = {3}, Pages = {1326 -}, Year = {1998}, url = {http://dx.doi.org/10.1116/1.590068}, Key = {98074283107} } @article{98074283101, Author = {Doolittle, William A. and Kropewnicki, Tom and Carter-Coman, C. and Stock, S. and Kohl, Paul and Jokerst, Nan Marie and Metzger, Robert A. and Kang, Sangbeom and Lee, Kyeong Kyun and May, Gary and Brown, April S.}, Title = {Growth of GaN on lithium gallate substrates for development of a GaN thin compliant substrate}, Journal = {Journal of Vacuum Science & Technology B: Microelectronics Processing and Phenomena}, Volume = {16}, Number = {3}, Pages = {1300 -}, Year = {1998}, url = {http://dx.doi.org/10.1116/1.590005}, Key = {98074283101} } @article{6118067, Author = {Doolittle, W.A. and Kropewnicki, T. and Carter-Coman, C. and Stock, S. and Kohl, P. and Jokerst, N.M. and Metzger, R.A. and Kang, S. and Lee, K. and May, G. and Brown, A.S.}, Title = {Growth of GaN on lithium gallate substrates for development of a GaN thin compliant substrate}, Journal = {Nitride Semiconductors Symposium}, Pages = {283 - 8}, Address = {Boston, MA, USA}, Year = {1998}, Keywords = {doping profiles;electron mobility;gallium compounds;III-V semiconductors;molecular beam epitaxial growth;semiconductor epitaxial layers;semiconductor growth;surface structure;thermal conductivity;thermally stimulated desorption;wide band gap semiconductors;X-ray diffraction;X-ray photoelectron spectra;}, Abstract = {The GaN on LGO system is the near perfect template (due to extremely high etch selectivity) for developing a viable thin film/compliant GaN substrate. Herein, we report on our efforts to grow GaN on LGO, including improvement of the microscopic surface morphology using pre-growth pretreatments. We also report on the first transferred thin film GaN substrate grown on LGO, transferred off of LGO, and mounted on GaAs. With this approach, (InAl)GaN alloys can be grown on thin GaN films, implementing a truly “compliant” substrate for the nitride alloy system. In addition, the flexibility of bonding to low cost Si, metal or standard ceramic IC packages is an attractive alternative to SiC and HVPE GaN substrates for optimizing cost verses thermal conductivity concerns. We have demonstrated high quality growth of GaN on LGO. X-ray rocking curves of 145 arc-seconds are obtained with only a 0.28 μm thick film. We present data on the out of plane crystalline quality of GaN/LGO material. Likewise, we show 2 orders of magnitude improvement in residual doping concentration and factors of 4 improvement in electron mobility as compared to the only previously reported electrical data. We show substantial vendor to vendor and intra-vendor LGO material quality variations. We have also quantified the desorption of Ga and Li from the surface of LGO at typical growth temperatures using in situ desorption mass spectroscopy and XPS}, Key = {6118067} } @article{6051166, Author = {Doolittle, W.A. and Kang, S. and Kropewnicki, T.J. and Stock, S. and Kohl, P.A. and Brown, A.S.}, Title = {MBE growth of high quality GaN on LiGaO2}, Journal = {J. Electron. Mater. (USA)}, Volume = {27}, Number = {8}, Pages = {58 - 60}, Year = {1998}, Keywords = {crystal structure;electron mobility;gallium compounds;III-V semiconductors;lithium compounds;molecular beam epitaxial growth;reflection high energy electron diffraction;semiconductor epitaxial layers;semiconductor growth;wide band gap semiconductors;}, Abstract = {We report on the growth of high structural quality (as determined by X-ray diffraction) GaN on a near lattice matched substrate, lithium gallate (LiGaO<sub>2</sub> or LGO). Low temperature growth conditions are described that result in very thin GaN films (<0.3 μm) with (0004) X-ray diffraction rocking curves full width at half maximum (FWHM) of 145 arc-sec and thicker films (1 μm) resulting in 85 arcsec FWHM. The effect of growth temperature is examined and found to result in a broad minimum in X-ray FWHM around 690°C. Detailed growth conditions and descriptions of the reflection high energy electron diffraction patterns observed during growth are given. Additionally, we report very highly resistive material and doped material with bulk electron mobilities in excess of 100 cm<sup>2</sup>/V-sec}, Key = {6051166} } @article{97093808201, Author = {Carter-Coman, Carrie and Bicknell-Tassius, Robert and Brown, April S. and Jokerst, Nan Marie}, Title = {Compliant substrates for reduction of strain relief in mismatched overlayers}, Journal = {Materials Research Society Symposium - Proceedings}, Volume = {441}, Pages = {361 - 366}, Address = {Boston, MA, USA}, Year = {1997}, Keywords = {Thin films;Mathematical models;Strain;Semiconducting indium compounds;Semiconducting gallium arsenide;Thickness measurement;Stress relief;}, Abstract = {Thin film compliant substrates can be used to extend the critical thickness in mismatched overlayers. A metastability model has been coupled with recent experimental strain relief data to determine the critical thickness of InGaAs epilayers grown on GaAs compliant substrates of variable thickness. The results of this model are also compared to other compliant substrate critical thickness models.}, Key = {97093808201} } @article{97033577369, Author = {Carter-Coman, Carrie and Bicknell-Tassius, Robert and Benz, Rudolph G. and Brown, April S. and Jokerst, Nan Marie}, Title = {Analysis of GaAs substrate removal etching with citric acid:H2O2 and NH4OH:H2O2 for application to compliant substrates}, Journal = {Journal of the Electrochemical Society}, Volume = {144}, Number = {2}, Pages = {29-31 -}, Year = {1997}, Keywords = {Semiconducting gallium arsenide;Substrates;Removal;Thin films;Acids;Semiconducting aluminum compounds;Refractive index;}, Abstract = {New properties associated with selective substrate removal have been observed in the application of this technique to GaAs thin film compliant substrates. Citric acid-and NH<sub>4</sub>OH-based etches are used to selectively etch the GaAs substrate and stop on an AlAs layer. The AlAs stop-etch layer is transformed into a layer that is almost twice as thick as the original layer, mismatched to the remaining GaAs epilayer, and has a refractive index around 2.0. Replacement of the single AlAs stop etch layer with multiple thin AlGaAs stop etch layers is proposed to alleviate this problem.}, Key = {97033577369} } @article{97083782542, Author = {Kromann, R.F. and Bicknell-Tassius, R.N. and Brown, A.S. and Dorsey, J.F. and Lee, K. and May, G.}, Title = {Real-time monitoring of RHEED using machine vision techniques}, Journal = {Journal of Crystal Growth}, Volume = {175-176}, Number = {pt 1}, Pages = {334 - 339}, Address = {Malibu, CA, USA}, Year = {1997}, url = {http://dx.doi.org/10.1016/S0022-0248(96)01184-0}, Keywords = {Semiconductor growth;Reflection high energy electron diffraction;Real time systems;Digital signal processing;Computer vision;Computer software;Computer hardware;Spurious signal noise;Substrates;Semiconductor quantum wells;Semiconducting gallium arsenide;Semiconductor device structures;}, Abstract = {A RHEED system has been developed that allows real-time monitoring of RHEED information throughout a multilayer growth run with rotation. The machine vision system consists of high-speed image capture hardware coupled with digital signal processing software that allows the real-time extraction/analysis of the RHEED intensity and width signals from the noise induced by substrate rotation. This system has been used to investigate the oxide desorption process on GaAs substrates, along with the specular spot intensity and width variation during the growth of a set of InGaAs/AlGaAs single quantum well structures with systematically varied process parameters. A strong correlation of the specular spot intensity with growth parameters has been observed. It is also shown that the observed specular spot intensity can be used to predict the quality of the InGaAs quantum well structures.}, Key = {97083782542} } @article{97103852384, Author = {Carter-Coman, Carrie and Bicknell-Tassius, Robert and Brown, April S. and Jokerst, Nan Marie}, Title = {Metastability modeling of compliant substrate critical thickness using experimental strain relief data}, Journal = {Applied Physics Letters}, Volume = {71}, Number = {10}, Pages = {1344 -}, Year = {1997}, url = {http://dx.doi.org/10.1063/1.119889}, Key = {97103852384} } @article{97123959032, Author = {Carter-Coman, Carrie and Brown, April S. and Metzger, Robert A. and Jokerst, Nan Marie and Pickering, Jason and Bottomley, Lawrence A.}, Title = {New mechanism for spontaneous nanostructure formation on bottom-patterned compliant substrates}, Journal = {Applied Physics Letters}, Volume = {71}, Number = {19}, Pages = {2773 -}, Year = {1997}, url = {http://dx.doi.org/10.1063/1.120129}, Key = {97123959032} } @article{5774401, Author = {Carter-Coman, C. and Bicknell-Tassius, R. and Brown, A.S. and Jokerst, N.M.}, Title = {Compliant substrates for reduction of strain relief in mismatched overlayers}, Journal = {Thin Films - Structure and Morphology. Symposium}, Pages = {361 - 6}, Address = {Boston, MA, USA}, Year = {1997}, Keywords = {deformation;gallium arsenide;III-V semiconductors;indium compounds;interface phenomena;internal stresses;semiconductor epitaxial layers;substrates;}, Abstract = {Thin film compliant substrates can be used to extend the critical thickness in mismatched overlayers. A metastability model has been coupled with recent experimental strain relief data to determine the critical thickness of InGaAs epilayers grown on GaAs compliant substrates of variable thickness. The results of this model are also compared to other compliant substrate critical thickness models}, Key = {5774401} } @article{98064238354, Author = {Doolittle, W.A. and Kropewnicki, T. and Carter-Coman, C. and Stock, S. and Kohl, P. and Jokerst, N.M. and Metzger, R.A. and Kang, S. and Lee, K. and May, G. and Brown, A.S.}, Title = {Growth of GaN on lithium gallate substrates for development of a GaN thin compliant substrate}, Journal = {Materials Research Society Symposium - Proceedings}, Volume = {482}, Pages = {283 - 288}, Address = {Boston, MA, USA}, Year = {1997}, Keywords = {Semiconductor growth;Substrates;Thin films;Morphology;Semiconductor doping;Desorption;Mass spectrometry;X ray photoelectron spectroscopy;Semiconducting films;Nitrides;}, Abstract = {The GaN on LGO system is the near perfect template (due to extremely high etch selectivity) for developing a viable thin film/compliant GaN substrate. Herein, we report on our efforts to grow GaN on LGO, including improvement of the microscopic surface morphology using pre-growth pretreatments. We also report on the first transferred thin film GaN substrate grown on LGO, transferred off of LOG, and mounted on GaAs. With this approach, (InAl)GaN alloys can be grown on thin GaN films, implementing a truly `compliant' substrate for the nitride alloy system. In addition, the flexibility of bonding to low cost Si, metal or standard ceramic IC packages is an attractive alternative to SiC and HVPE GaN substrates for optimizing cost verses thermal conductivity concerns. We have demonstrated high quality growth of GaN on LGO. X-Ray rocking curves of 145 arc-seconds are obtained with only a 0.28 µm thick film. We present data on the out of plane crystalline quality of GaN/LGO material. Likewise, we show 2 orders of magnitude improvement in residual doping concentration and factors of 4 improvement in electron mobility as compared to the only previously reported electrical data. We show substantial vendor to vendor and intra-vendor LGO material quality variations. We have also quantified the desorption of Ga and Li from the surface of LGO at typical growth temperatures using in situ desorption mass spectroscopy and XPS.}, Key = {98064238354} } @article{97083782684, Author = {Bicknell-Tassius, Robert N. and Lee, Kyeong and Brown, April S. and Dagnall, Georgianna and May, Gary}, Title = {Growth of AlGaAs-InGaAs quantum-well structures by molecular beam epitaxy: Observation of critical interdependent effects utilizing the design of experiments approach}, Journal = {Journal of Crystal Growth}, Volume = {175-176}, Number = {pt 2}, Pages = {1131 - 1137}, Address = {Malibu, CA, USA}, Year = {1997}, url = {http://dx.doi.org/10.1016/S0022-0248(96)01210-9}, Keywords = {Semiconducting aluminum compounds;Semiconducting indium compounds;Molecular beam epitaxy;Semiconductor growth;Statistical methods;Semiconducting gallium arsenide;Semiconductor device structures;}, Abstract = {The traditional approach to determine relationships between growth conditions and material properties has rested on the standard experimental approach - varying one parameter while holding all others constant. This technique does not effectively allow the observation of important interactions in complicated multilayer structures. Critical interdependent effects have been observed in the growth of AlGaAs/InGaAs quantum-well structures by molecular beam epitaxy (MBE). It is shown that statistical experimental design is an effective method for optimizing complex multilayer structures quickly. This technique is very useful for the optimization of processes with a large number of interdependent parameters and allows for the clear visualization and separation of complex interwoven effects. In the present work, we show for the first time the importance of the oxide desorption process for the optimal growth of AlGaAs-containing structures. The choice of an optimized oxide desorption process can lead to a decrease in the interfacial oxygen by almost two orders of magnitude.}, Key = {97083782684} } @article{97083782520, Author = {Fournier, Francoise and Metzger, Robert A. and Doolittle, Alan and Brown, April S. and Carter-Coman, Carrie and Jokerst, Nan Marie and Bicknell-Tassius, Robert}, Title = {Growth dynamics of InGaAs/GaAs by MBE}, Journal = {Journal of Crystal Growth}, Volume = {175-176}, Number = {pt 1}, Pages = {203 - 210}, Address = {Malibu, CA, USA}, Year = {1997}, url = {http://dx.doi.org/10.1016/S0022-0248(96)00888-3}, Keywords = {Semiconducting gallium arsenide;Semiconducting indium compounds;Semiconductor growth;Molecular beam epitaxy;Mass spectrometry;Activation energy;Thermal effects;Composition effects;Arsenic;Desorption;}, Abstract = {The growth dynamics of the InGaAs/GaAs system have been investigated by desorption mass spectrometry (DMS). Indium desorption spectra indicate the presence of one or two desorption mechanisms depending on the V/III beam equivalent pressure ratio. The activation energy associated with one of the desorption processes is found to be 1.3 eV and independent of V/III ratio and arsenic species. Analysis of the decay curve allows the calculation of the indium surface population during growth. This population is compared for the different growth conditions investigated. Indium incorporation coefficient curves as a function of substrate temperature are presented. Indium incorporation is found to be enhanced using high V/III ratio and the arsenic dimer, As<sub>2</sub>.}, Key = {97083782520} } @article{97053635881, Author = {Carter-Coman, Carrie and Bicknell-Tassius, Robert and Brown, April S. and Jokerst, Nan Marie}, Title = {Analysis of In0.07Ga0.93As layers on GaAs compliant substrates by double crystal x-ray diffraction}, Journal = {Applied Physics Letters}, Volume = {70}, Number = {13}, Pages = {1754 - 1756}, Year = {1997}, url = {http://dx.doi.org/10.1063/1.118647}, Keywords = {X ray crystallography;Semiconducting gallium arsenide;Crystal growth;Thin films;Bonding;Strain;Lattice constants;Calculations;Crystal defects;}, Abstract = {Five consecutive InGaAs-GaAs growths are conducted simultaneously on GaAs-based thin film compliant substrates and thick reference substrates using double crystal x-ray diffraction. The In<sub>0.07</sub>Ga<sub>0.93</sub>As layers are grown to thicknesses below and above the conventional critical thickness. It is found that InGaAs films grown on the compliant substrates have a larger critical thickness and slow strain relief than InGaAs grown on conventional substrates.}, Key = {97053635881} } @article{96013016387, Author = {Brown, A.S. and Bhattacharya, P. and Singh, J. and Zaman, P. and Sen, S. and Turco, F.}, Title = {Dependence of Al0.48In0.52As Schottky diode properties on molecular beam epitaxial growth temperature}, Journal = {Applied Physics Letters}, Volume = {68}, Number = {2}, Pages = {220 -}, Year = {1996}, url = {http://dx.doi.org/10.1063/1.116466}, Key = {96013016387} } @article{96083280775, Author = {Carter-Coman, Carrie and Brown, April S. and Bicknell-Tassius, Robert and Jokerst, Nan Marie and Allen, Mark}, Title = {Strain-modulated epitaxy: a flexible approach to 3-D band structure engineering without surface patterning}, Journal = {Applied Physics Letters}, Volume = {69}, Number = {2}, Pages = {257 -}, Year = {1996}, url = {http://dx.doi.org/10.1063/1.117942}, Key = {96083280775} } @article{96073255513, Author = {Carter-Coman, Carrie and Brown, April S. and Bicknell-Tassius, Robert and Jokerst, Nan Marie and Fournier, Francoise and Dawson, Douglas E.}, Title = {Strain-modulated epitaxy: modification of growth kinetics via patterned, compliant substrates}, Journal = {Journal of Vacuum Science & Technology B: Microelectronics Processing and Phenomena}, Volume = {14}, Number = {3}, Pages = {2170 -}, Year = {1996}, url = {http://dx.doi.org/10.1116/1.588892}, Key = {96073255513} } @article{97013489581, Author = {Cat, Huy H. and Gentile, Antonio and Eble, John C. and Lee, Myunghee and Vendier, Olivier and Joo, Young Joong and Wills, D. Scott and Brooke, Martin and Jokerst, Nan Marie and Brown, April S.}, Title = {SIMPil: An OE integrated SIMD architecture for focal plane processing applications}, Journal = {International Conference on Massively Parallel Processing Using Optical Interconnections (MPPOI), Proceedings}, Pages = {44 - 52}, Address = {Maui, HI, USA}, Year = {1996}, url = {http://dx.doi.org/10.1109/MPPOI.1996.559035}, Keywords = {Digital signal processing;Thin film devices;Integrated optoelectronics;Image processing;Edge detection;Image compression;Computer architecture;}, Abstract = {Focal plane processing applications present a growing computing need for portable telecomputing and videoputing systems. This paper demonstrates the integration of digital processing, analog interface circuitry, and thin film OE devices into a compact computing package. The SIMPil architecture provides a programmable, silicon efficient SIMD processor for effective execution of early image processing applications such as edge detection, convolution, and compression. Results from a demonstration SIMPil node are presented including its microarchitecture, and performance on image processing applications.}, Key = {97013489581} } @article{96083301631, Author = {Carter-Coman, C. and Brown, A.S. and Jokerst, N.M. and Dawson, D.E. and Bicknell-Tassius, R. and Feng, Z.C. and Rajkumar, K.C. and Dagnall, G.}, Title = {Strain accommodation in mismatched layers by molecular beam epitaxy: Introduction of a new compliant substrate technology}, Journal = {Journal of Electronic Materials}, Volume = {25}, Number = {7}, Pages = {1044 - 1048}, Year = {1996}, Keywords = {Substrates;Strain;Growth (materials);Kinetic theory;Epitaxial growth;Thin films;}, Abstract = {Compliant substrates allow a new approach to the growth of strained epitaxial layers, in which part of the strain is accommodated in the substrate. In this article compliant substrates are discussed and a new compliant substrate technology based on bonded thin flim substrates is introduced. This technology has several advantages over previously published methods, including the ability to pattern both the top and bottom of the material. A new concept enabled by this compliant substrate technology, strain modulated epitaxy, will be introduced. Using this technique, the properties of the semiconductor material can be controlled laterally across a substrate. Results of two experiments are presented in which low composition In<sub>x</sub>Ga<sub>1-x</sub>As was grown by molecular beam epitaxy on GaAs compliant substrates at thicknesses both greater than and less than the conventional critical thickness. It was found that for t gt; t<sub>c</sub>, there was an inhibition of defect production in the epitaxial films grown on the compliant substrates as compared to those grown on conventional reference substrates. For t < t<sub>c</sub>, photoluminescence and x-ray diffraction show the compliant substrates to be of excellent quality and uniformity as compared to conventional substrates.}, Key = {96083301631} } @article{5324747, Author = {Gilbert, E.P. and Reynolds, P.A. and Brown, A.S. and White, J.W.}, Title = {n-paraffin solid solutions: modification of phase separation with carbon number}, Journal = {Chem. Phys. Lett. (Netherlands)}, Volume = {255}, Number = {4-6}, Pages = {373 - 7}, Year = {1996}, url = {http://dx.doi.org/10.1016/0009-2614(96)00371-5}, Keywords = {density;neutron diffraction;organic compounds;solid solutions;}, Abstract = {Small-angle neutron scattering is used to monitor microphase formation in the solid state in equimolar binary hydrocarbon systems C<sub>n</sub>H<sub>2n+2</sub>:C<sub>m</sub>D<sub>2m+2</sub> for selected n=20-34 and m=36. Microphase formation is maximum for n=28 and negligible for n=20, 32 and 34. n=30 is found to be intermediate. These observations are explicable in terms of increasing molar volume differences between the two components forming the mixture. As the chain length difference increases, the formation of a lamellar microphase occurs in preference to a continuous solid solution until this is itself overtaken by two-phase separation}, Key = {5324747} } @article{95062757008, Author = {Cat, Huy H. and Wills, D. Scott and Jokerst, Nan Marie and Brooke, Martin A. and Brown, April S.}, Title = {Three-dimensional, massively parallel, optically interconnected silicon computational hardware and architectures for high-speed IR scene generation}, Journal = {Proceedings of SPIE - The International Society for Optical Engineering}, Volume = {2469}, Pages = {141 - 145}, Address = {Orlando, FL, USA}, Year = {1995}, url = {http://dx.doi.org/10.1117/12.210584}, Keywords = {Optical interconnects;Performance;Thin films;Optoelectronic devices;Semiconducting silicon;Integrated circuits;Parallel processing systems;Semiconducting indium compounds;Manufacture;Testing;Cost effectiveness;}, Abstract = {High frame rate infrared scene generation depends on high performance digital processors that are tightly coupled to infrared emitter arrays. Massively parallel image generation hardware can realize the type of high throughput, high frame rate processing that will characterize the next generation of scene generators. This work outlines projects in massively parallel, high throughput image generation hardware using thin film optoelectronic devices which are integrated directly onto low cost silicon integrated circuits. For basic scene generation, an array of thin film emitters are placed on top of digital single instruction stream, multiple data stream (SIMD) parallel processors to provide high performance focal plane generation in a monolithic system. For more complex scene generation, low cost stacked silicon integrated circuits, using through-silicon wafer optoelectronic channels for three dimensional interconnections, form an extremely dense, high throughput, three dimensional parallel processing system. Thin film InGaAsP devices, which operate at wavelengths to which silicon is transparent, are integrated on top of standard foundry silicon integrated circuits so that stacked processor chips can communicate vertically. High speed analog interface circuitry on the Si integrated circuits provides a high bandwidth link between the devices and the digital processing circuitry. This processing approach provides tremendous generality for high frame rate image generation applications in a compact system. Issues addressed include system interfacing, power management, manufacturing tolerances, testing and repair, and system cost and effectiveness.}, Key = {95062757008} } @article{95052696922, Author = {Rosenbaum, Steven E. and Kormanyos, Brian K. and Jelloian, Linda M. and Matloubian, Mehran and Brown, April S. and Larson, Lawrence E. and Nguyen, Loi D. and Thompson, Mark A. and Katehi, Linda P.B. and Rebeiz, Gabriel M.}, Title = {155- and 213-GHz AlInAs/GaInAs/InP HEMT MMIC oscillators}, Journal = {IEEE Transactions on Microwave Theory and Techniques}, Volume = {43}, Number = {4 pt 2}, Pages = {927 - 933}, Address = {Ann Arbor, MI, USA}, Year = {1995}, url = {http://dx.doi.org/10.1109/22.375256}, Keywords = {Monolithic microwave integrated circuits;Semiconducting gallium arsenide;Semiconducting aluminum compounds;Semiconducting indium phosphide;Electric charge;Gates (transistor);Semiconductor device manufacture;Micrometers;Electron beams;Slot antennas;Molecular beam epitaxy;High electron mobility transistors;}, Abstract = {We report on the design and measurement of monolithic 155- and 213-GHz quasi-optical oscillators using AlInAs/GaInAs/InP HEMT's. These results are believed to be the highest frequency three-terminal oscillators reported to date. The indium concentration in the channel was 80% for high sheet charge and mobility. The HEMT gates were fabricated with self-aligned sub-tenth-micrometer electron-beam techniques to achieve gate lengths on the order of 50 nm and drain-source spacing of 0.25 μm. Planar antennas were integrated into the fabrication process resulting in a compact and efficient quasi-optical Monolithic Millimeter-wave Integrated Circuit (MMIC) oscillator.}, Key = {95052696922} } @article{94071336131, Author = {Brown, A.S. and Schmitz, A.E. and Nguyen, L.D. and Henige, J.A. and Larson, L.E.}, Title = {Growth of high performance InxGa1-xAs (.52 < x <.9) - (Al.48In.52As) high electron mobility transistors by MBE}, Journal = {IEEE International Conferece on Indium Phosphide and Related Materials}, Pages = {263 - 266}, Address = {Santa Barbara, CA, USA}, Year = {1994}, url = {http://dx.doi.org/10.1109/ICIPRM.1994.328217}, Keywords = {Semiconducting indium compounds;Semiconductor growth;Electron transport properties;Semiconductor device structures;Molecular beam epitaxy;Semiconductor doping;Phase transitions;Crystal lattices;Gates (transistor);Relaxation processes;Electron transitions;High temperature operations;}, Abstract = {The paper reports the successful attempts at significantly improving the electron mobility in thin channel, device structures with high two-dimensional electron gas (2DEG) concentrations. InGaAs-AlInAs modulation-doped structures were grown by MBE in a Riber 2300 system on (100)-oriented InP substrates. The highest room temperature mobility achieved to date for low sheet charge and high sheet charge samples were realized in a structure with a 10nm 80% In channel utilizing a stress-compensation prelayer.}, Key = {94071336131} } @article{4620585, Author = {Schramm, J.E. and Hu, E.L. and Merz, J.L. and Brown, J.J. and Melendes, M.A. and Thompson, M.A. and Brown, A.S.}, Title = {Highly selective reactive ion etch process for InP-based device fabrication using methane/hydrogen/argon}, Journal = {J. Vac. Sci. Technol. B, Microelectron. Process. Phenom. (USA)}, Volume = {11}, Number = {6}, Pages = {2280 - 3}, Address = {San Diego, CA, USA}, Year = {1993}, url = {http://dx.doi.org/10.1116/1.586890}, Keywords = {aluminium compounds;gallium arsenide;high electron mobility transistors;III-V semiconductors;indium compounds;sputter etching;}, Abstract = {The etch rates of GaInAs and AlInAs were characterized using a mixture of methane, hydrogen, and argon as a function of self-bias voltage. Effectively infinite etch selectivity between GaInAs and AlInAs was found for voltages below 200 V. This highly selective etch process was applied to the gate recess of a high electron mobility transistor device, and preliminary device measurements were made}, Key = {4620585} } @article{4604389, Author = {Brown, J.J. and Brown, A.S. and Rosenbaum, S.E. and Schmitz, A.S. and Matloubian, M. and Larson, L.E. and Melendes, M.A. and Thompson, M.A.}, Title = {Study of the dependence of Ga0.47In0.53As/Alx In1-xAs power HEMT breakdown voltage on Schottky layer design and device layout}, Journal = {IEEE Trans. Electron Devices (USA)}, Volume = {40}, Number = {11}, Pages = {2111 - 12}, Address = {Santa Barbara, CA, USA}, Year = {1993}, url = {http://dx.doi.org/10.1109/16.239781}, Keywords = {aluminium compounds;electric breakdown of solids;gallium arsenide;high electron mobility transistors;III-V semiconductors;indium compounds;power transistors;Schottky effect;solid-state microwave devices;}, Abstract = {Summary form only given. A systematic study of the improvement of Ga<sub>0.47</sub>In<sub>0.53</sub>As/Al<sub>x</sub> In<sub>1-x</sub>As HEMT (high electron mobility transistor) breakdown voltage by varying the Schottky layer design and device geometry is presented. The HEMT structure investigated is a modulation-doped Ga<sub>0.47</sub>In<sub>0.53</sub>As/Al<sub>x</sub> In<sub>1-x</sub>As on InP device with a sheet of charge placed at the center of the 300 Å wide channel. The device with a gate length of 0.5 μm, a source-drain spacing of 5μm, and an Al<sub>0.7</sub>In<sub>0.3</sub>As Schottky layer exhibited the best breakdown characteristics of |BV<sub>gd</sub>|=6.8 V and BV<sub>ds</sub>=7.8 V. The typical transistor had a maximum transconductance of 500 mS/mm, a full channel current of 700 mA/mm for a gate bias of 0.4 V, and a current gain cutoff frequency of over 80 GHz. The power performance was measured on 500-μm-wide devices at 4 GHz and V<sub>ds</sub>=4.5 V. Under Class AB operating conditions, the output power density, power-added efficiency, and power gain were 0.45 W/mm, 59%, and 14.25 dB, respectively}, Key = {4604389} } @article{93040774349, Author = {Matloubian, Mehran and Brown, April S. and Nguyen, Loi D. and Melendes, Melissa A. and Larson, Lawrence E. and Delaney, Michael J. and Pence, John E. and Rhodes, Richard A. and Thompson, Mark A. and Henige, Joseph A.}, Title = {High-power V-band AlInAs/GaInAs on InP HEMT's}, Journal = {IEEE Electron Device Letters}, Volume = {14}, Number = {4}, Pages = {188 - 189}, Year = {1993}, url = {http://dx.doi.org/10.1109/55.215155}, Keywords = {Semiconducting indium phosphide;Semiconducting aluminum compounds;Semiconducting gallium compounds;}, Abstract = {We report on the dc and RF performance of δ-doped channel AlInAs/GaInAs on InP power HEMT's. A 450-μm-wide device with a gate length of 0.22 μm has achieved an output power of 150 mW (at the 1-dB gain compression point) with power-added efficiency of 20% at 57 GHz. The device has a saturated output power of 200 mW with power-added efficiency of 17%. This is the highest output power measured from a single InP-based HEMT at this frequency, and demonstrates the feasibility of these HEMT's for high-power applications in addition to low-noise applications at V band.}, Key = {93040774349} } @article{94061318557, Author = {Rosenbaum, Steven E. and Jelloian, Linda M. and Brown, April S. and Thompson, Mark A. and Matloubian, Mehran and Larson, Lawrence E. and Lohr, Ross and Kormanyos, Brian K. and Rebeiz, Gabriel M. and Katehi, Linda P.B.}, Title = {213 GHz AlInAs/GaInAs/InP HEMT MMIC oscillator}, Journal = {Technical Digest - International Electron Devices Meeting}, Pages = {924 - 926}, Address = {Washington, DC, USA}, Year = {1993}, url = {http://dx.doi.org/10.1109/IEDM.1993.347470}, Keywords = {Equivalent circuits;Molecular beam epitaxy;Field effect transistors;Heterojunctions;Substrates;}, Abstract = {We have fabricated submillimeter-wave MMIC oscillator circuits using AlInAs/GaInAs/ HEMTs on InP substrates, which have resulted in oscillators operating at fundamental frequencies of 155 and 213 GHz. These results are believed to be the highest frequency three-terminal oscillators reported to date.}, Key = {94061318557} } @article{93101118299, Author = {Rosenbaum, Steven E. and Jelloian, Linda M. and Larson, Lawrence E. and Mishra, Umesh K. and Pierson, Deborah A. and Thompson, Mark S. and Liu, Takyiu and Brown, April S.}, Title = {2-GHz three-stage AlInAs-GaInAs-InP HEMT MMIC low-noise amplifier}, Journal = {IEEE Microwave and Guided Wave Letters}, Volume = {3}, Number = {8}, Pages = {265 - 267}, Year = {1993}, url = {http://dx.doi.org/10.1109/75.242220}, Keywords = {High electron mobility transistors;Monolithic integrated circuits;Microwave devices;Spurious signal noise;Signal to noise ratio;Semiconductor device manufacture;Semiconducting indium phosphide;Semiconducting aluminum compounds;Semiconducting gallium arsenide;Semiconductor device structures;Electric losses;Performance;}, Abstract = {A three-stage monolithic microwave integrated circuit (MMIC) low-noise amplifier (LNA) has been fabricated using 0.15-μm gate-length InP-based (AlInAs-GaInAs) high electron mobility transistor (HEMT) technology. The LNA exhibited less than 0.5-dB noise figure and greater than 35-dB gain from 2.25 to 2.5 GHz. The input and output return loss exceeded 15 dB across the band. These results are believed to be the best reported to date from a MMIC amplifier in this frequency range.}, Key = {93101118299} } @article{93051596049, Author = {Brown, A.S. and Henige, J.A. and Schmitz, A.E. and Larson, L.E.}, Title = {Effect of growth conditions on the electrical and optical properties of AlxIn1-xAs (0.48 < x < 0.7)-Ga0.47In0.53As heterostructures}, Journal = {Applied Physics Letters}, Volume = {62}, Number = {1}, Pages = {66 -}, Year = {1993}, url = {http://dx.doi.org/10.1063/1.108821}, Key = {93051596049} } @article{94041255772, Author = {Matloubian, Mehran and Jelloian, Linda M. and Brown, April S. and Nguyen, Loi D. and Larson, Lawrence E. and Delaney, M.J. and Thompson, Mark A. and Rhodes, R.A. and Pence, J.E.}, Title = {V-band high-efficiency high-power AlInAs/GaInAs/InP HEMT's}, Journal = {IEEE Transactions on Microwave Theory and Techniques}, Volume = {41}, Number = {12}, Pages = {2206 - 2210}, Year = {1993}, url = {http://dx.doi.org/10.1109/22.260707}, Keywords = {Semiconducting indium phosphide;Performance;Microwave devices;Semiconductor device structures;Semiconductor doping;Gates (transistor);Concentration (process);Semiconducting aluminum compounds;Semiconducting gallium compounds;Molecular beam epitaxy;Semiconductor device manufacture;Ohmic contacts;}, Abstract = {In this paper, we report on the state-of-the-art power performance of InP-based HEMT's at V-band. Power HEMT's were fabricated using two different material layer structures. The power performances of these HEMT's were measured at 59 GHz. We were able to achieve an output power of 155 mW with 4.9 dB gain, and power-added efficiency of 30 percent from a 448-μm-wide HEMT fabricated on a δ-doped channel layer structure. By using a double-doped layer structure, we were able to achieve an output power of 145 mW with 4.2 dB gain, and power-added efficiency of 24 percent. Output power of 288 mW with 3.6 dB gain and power-added efficiency of 20.4 percent were obtained by power combining two of the δ-doped channel HEMT's. These combinations of output power and efficiency are the best reported to date for InP-based HEMT's, and are comparable to the best results reported for AlGaAs/InGaAs on GaAs pseudomorphic HEMT's at this frequency.}, Key = {94041255772} } @article{93071032443, Author = {Matloubian, M. and Brown, A.S. and Nguyen, L.D. and Melendes, M.A. and Larson, L.E. and Delaney, M.J. and Thompson, M.A. and Rhodes, R.A. and Pence, J.E.}, Title = {20-GHz high-efficiency AlInAs-GaInAs on InP power HEMT}, Journal = {IEEE Microwave and Guided Wave Letters}, Volume = {3}, Number = {5}, Pages = {142 - 144}, Year = {1993}, url = {http://dx.doi.org/10.1109/75.217211}, Keywords = {Semiconducting aluminum compounds;Semiconducting indium compounds;Semiconducting gallium arsenide;Power amplifiers;Gain measurement;Electric power measurement;}, Abstract = {A single stage 20-GHz power amplifier was developed using double-doped AlInAs-GaInAs on InP HEMT. Output power of 516 mW (0.645 W/mm) with power-added efficiency of 47.1% with 7.1-dB gain were obtained from an 800-μm wide device. The device had a saturated output power of more than 560 mW (0.7 W/mm). This is believed to be the highest combination of output power, power density, gain, and power-added efficiency reported for an InP-based FET at this frequency.}, Key = {93071032443} } @article{94041266192, Author = {Larson, L.E. and Matloubian, M.M. and Brown, J.J. and Brown, A.S. and Rhodes, R. and Crampton, D. and Thompson, M.}, Title = {AlInAs/GaInAs on InP HEMTs for low power supply voltage operation of high power-added efficiency microwave amplifiers}, Journal = {Electronics Letters}, Volume = {29}, Number = {15}, Pages = {1324 - 1326}, Year = {1993}, Keywords = {Microwave amplifiers;Semiconducting indium phosphide;Power amplifiers;Semiconducting aluminum compounds;Semiconducting gallium compounds;Performance;Millimeter waves;Electric power supplies to apparatus;}, Abstract = {High power-added efficiency microwave power amplifier results are reported for AlInAs/GaInAs on InP HEMTs operated at relatively low power supply voltages (2.5-3 V). C-band power amplifiers are reported with power-added efficiencies as high as 67%, and output powers between 200 and 300 mW. This excellent performance at low power supply voltages is attributed to the high gain and low access resistances of the devices, which leads to a high drain efficiency despite the low power supply voltage.}, Key = {94041266192} } @article{94061322240, Author = {Zakharov, N.D. and Liliental-Weber, Z. and Swider, W. and Brown, A.S. and Metzger, R.}, Title = {Structure of Ga0.47In0.53As epitaxial layers grown on InP substrates at different temperatures}, Journal = {Applied Physics Letters}, Volume = {63}, Number = {20}, Pages = {2809 -}, Year = {1993}, url = {http://dx.doi.org/10.1063/1.110294}, Key = {94061322240} } @article{93101087705, Author = {Matloubian, M. and Jelloian, L.M. and Brown, A.S. and Nguyen, L.D. and Larson, L.E. and Delaney, M.J. and Thompson, M.A. and Rhodes, R.A. and Pence, J.E.}, Title = {V-band high-efficiency high-power AlInAs/GaInAs/InP HEMTs}, Journal = {IEEE MTT-S International Microwave Symposium Digest}, Volume = {2}, Pages = {535 - 537}, Address = {Atlanta, GA, USA}, Year = {1993}, url = {http://dx.doi.org/10.1109/MWSYM.1993.276882}, Keywords = {Performance;Semiconducting indium phosphide;Semiconducting gallium compounds;Semiconductor device structures;}, Abstract = {In this paper we report on the stage-of-the-art power performance of InP-based HEMTs at 59 GHz. Using a 448 μm wide HEMT with a gate-length of 0.15 μm, an output power of 155 mW with 4.9 dB gain, and power-added efficiency of 30.1% were obtained. By power combining two of these HEMTs we were able to achieve an output power of 288 mW with 3.6 dB gain and power-added efficiency of 20.4%. This is the highest output power reported with such a high-efficiency for InP-based HEMTs, and is comparable to the best results reported for AlGaAs/InGaAs on GaAs pseudomorphic HEMTs at this frequency.}, Key = {93101087705} } @article{94011191194, Author = {Zakharov, N.D. and Liliental-Weber, Z. and Swider, W. and Washburn, J. and Brown, A.S. and Metzger, R.}, Title = {Ordering in InGaAs/InAlAs layers}, Journal = {Journal of Electronic Materials}, Volume = {22}, Number = {12}, Pages = {1495 - 1498}, Year = {1993}, Keywords = {Semiconducting gallium arsenide;Semiconducting indium compounds;Crystal structure;Crystal lattices;Transmission electron microscopy;Order disorder transitions;}, Abstract = {The structure of InGaAs/InAlAs layers lattice matched to an InP substrate, grown on either (100) or on (110) with a 4° tilt toward [111 over-bar ] at 500 and 300°C has been investigated by transmission electron microscopy. High perfection resulted for the layers grown on [001] oriented substrates whereas growth on the near [110] substrates resulted in compositional nonuniformities, macrosteps formation, and ordering of the group III elements. This difference in structural perfection between the two sets of samples was also reflected in differences in electrical properties.}, Key = {94011191194} } @article{4466016, Author = {Nguyen, L.D. and Brown, A.S. and Thompson, M.A. and Jelloian, L.M.}, Title = {50 nm InP high electron mobility transistors}, Journal = {Microw. J. (USA)}, Volume = {36}, Number = {6}, Pages = {96, 98, 101 -}, Year = {1993}, Keywords = {high electron mobility transistors;III-V semiconductors;indium compounds;semiconductor device noise;solid-state microwave devices;}, Abstract = {A new type of field-effect transistor (FET), the indium phosphide high electron mobility transistor (InP HEMT), has recently emerged as an attractive candidate for low noise applications at microwave and MM-wave frequencies. It exhibits the lowest noise figures (<1 dB at 60 GHz), and the highest cutoff frequencies (>300 GHz) among all three-terminal semiconductor devices. Also, it is the only type of transistor that has shown useful gain at frequencies above 100 GHz (7.3 dB at 140 GHz). The authors describe the scaling of InP HEMTs down to 50 nm gate length. By properly designing the HEMT epitaxial layer and scaling its parasitic resistances, significant improvements in device performance are possible for FETs with gate lengths as short as 50 nm. With further optimization, 50 nm InP HEMTs should extend the operating frequency of three-terminal semiconductor devices to at least 300 GHz, as well as provide a low cost alternative to ultra low noise masers and SIS mixers at microwave frequencies}, Key = {4466016} } @article{4469034, Author = {Metzger, R.A. and Brown, A.S. and McCray, L.G. and Henige, J.A.}, Title = {Structural and electrical properties of low temperature GaInAs}, Journal = {J. Vac. Sci. Technol. B, Microelectron. Process. Phenom. (USA)}, Volume = {11}, Number = {3}, Pages = {798 - 801}, Address = {Ottawa, Ont., Canada}, Year = {1993}, url = {http://dx.doi.org/10.1116/1.586792}, Keywords = {electronic conduction in crystalline semiconductor thin films;gallium arsenide;III-V semiconductors;indium compounds;molecular beam epitaxial growth;secondary ion mass spectra;semiconductor epitaxial layers;semiconductor growth;X-ray diffraction examination of materials;}, Abstract = {GaInAs lattice matched to InP was grown by molecular-beam epitaxy over a temperature range of 100-450°C and characterized by X-ray diffraction, resistivity, and secondary ion mass spectroscopy, X-ray diffraction analysis indicated the incorporation of excess As for samples grown below 250°C. As-grown GaInAs was <i>n</i>-type with electrical concentration increasing with decreasing growth temperature, ranging from 5×10<sup>14</sup> cm<sup>-3</sup> (450°C) to 1.8×10<sup>17</sup> (150°C). Secondary ion mass spectroscopy indicated that this behavior was not due to the incorporation of background <i>n</i>-type dopants. Be- and Si-doped GaInAs at 5×10<sup>18</sup> cm<sup>-3</sup> showed full electrical activation for growth temperatures down to 260°C, with only partial activation for Si and no activation for Be for growth temperatures below 260°C}, Key = {4469034} } @article{4469039, Author = {Brown, A.S. and Metzger, R.A. and Henige, J.A.}, Title = {Growth and properties of AlInAs-GaInAs alloys and quantum wells on (110)InP}, Journal = {J. Vac. Sci. Technol. B, Microelectron. Process. Phenom. (USA)}, Volume = {11}, Number = {3}, Pages = {817 - 19}, Address = {Ottawa, Ont., Canada}, Year = {1993}, url = {http://dx.doi.org/10.1116/1.586753}, Keywords = {aluminium compounds;gallium arsenide;III-V semiconductors;indium compounds;luminescence of inorganic solids;molecular beam epitaxial growth;photoluminescence;semiconductor growth;semiconductor quantum wells;spectral line breadth;}, Abstract = {GaInAs and AlInAs structures have been grown on on-axis and misoriented [4°-(111) In-plane] (110) InP substrates. In general, the growth on the on-axis substrates shows a high density of defects; while the surface morphology using misoriented substrates is smooth. A smooth morphology is obtained on on-axis (110) InP, however, with a low substrate temperature and high V/III ratio. The photoluminescence properties of the individual alloys grown on (110) show high intensities, similar to that which can be obtained on (100) substrates, but the peaks are significantly broadened and shifted in energy. The interface quality of the GaInAs-AlInAs (110) heterojunction, inferred from the linewidths of quantum well emissions, is improved by growing at higher temperature}, Key = {4469039} } @article{4306656, Author = {Kiziloglu, K. and Hashemi, M.M. and Lie-Wei Yin and Yuan Jing Li and Petroff, P.M. and Mishra, U.K. and Brown, A.S.}, Title = {Rapid thermal annealing characteristics of bulk AlInAs/nP and AlInAs/GaInAs/InP high electron mobility transistor structures with planar silicon doping}, Journal = {J. Appl. Phys. (USA)}, Volume = {72}, Number = {8}, Pages = {3798 - 802}, Year = {1992}, url = {http://dx.doi.org/10.1063/1.352277}, Keywords = {aluminium compounds;annealing;carrier density;carrier mobility;diffusion in solids;gallium arsenide;high electron mobility transistors;III-V semiconductors;indium compounds;rapid thermal processing;semiconductor doping;silicon;two-dimensional electron gas;vacancies (crystal);}, Abstract = {The effects of high temperature rapid thermal annealing processes on carrier concentration and mobility of bulk AlInAs and AlInAs/GaInAs high electron mobility transistor structures with planar Si doping are studied. At annealing temperatures of 700°C and 800°C, slight reduction in mobilities and carrier concentration are observed in samples annealed with a Si<sub>3</sub>N<sub>4</sub> cap or GaAs pieces in close proximity. The reduction in mobility is thought to be due to enhanced diffusion of the donor Si atoms towards the two-dimensional electron gas channel. Preferential vacancy enhanced diffusion of Si atoms towards the surface is projected to be responsible for the loss in carrier concentration. At these annealing temperatures, the reduction in mobility in the samples annealed with SiO<sub>2</sub> capping is more pronounced, and is as high as 80% at the measurement temperature of 15 K. This behavior is attributed to the outdiffusion of Ga and In atoms into the oxide thereby creating vacancies and resulting in interface mixing. Reduction in mobility and carrier concentration are much more substantial in the 900°C anneals done with Si<sub>3</sub>N<sub>4</sub> cap and GaAs pieces in close proximity. This indicates the destruction of the heterostructure integrity of the AlInAs/GaInAs interface. For the particular anneal with a SiO<sub>2</sub> cap at this temperature, the carrier concentration increases above its reference value due to effective doping of the ternary material by the back-diffusion Si atoms from the SiO<sub>2</sub> cap}, Key = {4306656} } @article{93020691591, Author = {Nguyen, Loi D. and Brown, April S. and Thompson, Mark A. and Jelloian, Linda M.}, Title = {50-nm self-aligned-gate pseudomorphic AlInAs/GaInAs high electron mobility transistors}, Journal = {IEEE Transactions on Electron Devices}, Volume = {39}, Number = {9}, Pages = {2007 - 2014}, Year = {1992}, url = {http://dx.doi.org/10.1109/16.155871}, Keywords = {Semiconducting aluminum compounds;Semiconducting gallium compounds;Integral equations;Gates (transistor);}, Abstract = {The design and fabrication of a class of 50-nm self-aligned-gate pseudomorphic AlInAs/GaInAs high electron mobility transistors (HEMTs) with potential for ultra-high-frequency and ultra-low-noise applications are reported. These devices exhibit an extrinsic transconductance of 1740 mS/mm and an extrinsic current-gain cutoff frequency of 340 GHz at room temperature. The small-signal characteristics of a pseudomorphic and a lattice-matched AlInAs/GaInAs HEMT with similar gate length (50 nm) and gate-to-channel separation (17.5 nm) are compared. The former demonstrates a 16% higher transconductance and a 15% higher current-gain cutoff frequency, but exhibits a 38% poorer output conductance. An analysis of the high-field transport properties of ultra-short gate-length AlInAs/GaInAs HEMTs shows that a reduction of gate length from 150 to 50 nm neither enhances nor reduces their average velocity. In contrast, the addition of indium from 53% to 80% improves this parameter by 19%.}, Key = {93020691591} } @article{95052701812, Author = {Brown, A.S. and Nguyen, L.D. and Metzger, R.A. and Matloubian, M. and Schmitz, A.E. and Lui, M. and Wilson, R.G. and Henige, J.A.}, Title = {Reduced silicon movement in GalnAs/AlInAs HEMT structures with low temperature AlInAs spacers}, Pages = {281 - 286}, Address = {Seattle, WA, USA}, Year = {1992}, Key = {95052701812} } @article{92040460892, Author = {Nguyen, Loi D. and Brown, April S. and Thompson, Mark A. and Jelloian, Linda M. and Larson, Larry E. and Matloubian, Mehran}, Title = {650-angstrom self-aligned-gate pseudomorphic Al0.48In0.52As/Ga0.20In0.80As high electron mobility transistors}, Journal = {IEEE Electron Device Letters}, Volume = {13}, Number = {3}, Pages = {143 - 145}, Year = {1992}, url = {http://dx.doi.org/10.1109/55.144991}, Keywords = {Semiconducting Aluminum Compounds--Applications;Transistors, High Electron Mobility--Fabrication;Semiconducting Indium Compounds--Applications;Semiconducting Gallium Compounds--Applications;}, Abstract = {The authors report on the design and fabrication of a 650-angstrom self-aligned-gate pseudomorphic Al<sub>0.48</sub>In<sub>0.52</sub>As/Ga<sub>0.20</sub>In<sub>0.80</sub>As high electron mobility transistor (HEMT) with a state-of-the-art current gain cutoff frequency of over 300 GHz. This work clearly demonstrates the potential of sub-0.1-μm gate-length HEMTs for near-future microwave and millimeter-wave applications.}, Key = {92040460892} } @article{4547745, Author = {Metzger, R.A. and Brown, A.S. and Wilson, R.G. and Liu, T. and Stanchina, W.E. and Nguyen, L.D. and Schmitz, A.E. and McCray, L.G. and Henige, J.A.}, Title = {The use of low temperature AlInAs and GaInAs lattice matched to InP in the fabrication of HBTs and HEMTs}, Journal = {Low Temperature (LT) GaAs and Related Materials Symposium}, Pages = {259 - 64}, Address = {Boston, MA, USA}, Year = {1992}, Keywords = {aluminium compounds;gallium arsenide;heterojunction bipolar transistors;high electron mobility transistors;III-V semiconductors;indium compounds;molecular beam epitaxial growth;semiconductor growth;}, Abstract = {AlInAs and GaInAs lattice matched to InP and grown by MBE over a temperature range of 200 to 350°C (normal growth temperature of 500°C) has been used to enhance the device performance of inverted (where the donor layer lies below the channel) High Electron Mobility Transistors (HEMTs) and Heterojunction Bipolar Transistors (HBTs), respectively. The authors show that an AlInAs spacer grown over a temperature range of 300 to 350°C and inserted between the AlInAs donor layer and GaInAs channel significantly reduces Si movement from the donor layer into the channel. This produces an inverted HEMT with a channel charge of 3.0×10<sup>12</sup> cm<sup>-2</sup> and mobility of 9131 cm<sup>2</sup>/V-s, as compared to the same HEMT with a spacer grown at 500°C resulting in a channel charge of 2.3×10<sup>12</sup> cm<sup>-2</sup> and mobility of 4655 cm<sup>2</sup>/V-s. They also show that a GaInAs spacer grown over a temperature range of 300 to 350°C and inserted between the AlInAs emitter and GaInAs base of an npn HBT significantly reduces Be movements from the base into the emitter, thereby allowing higher Be base dopings (up to 1×10<sup>20</sup> cm<sup>-3</sup>) confined to 500 Å base widths, resulting in an AlInAs/GaInAs HBT with an f<sub>max</sub> of 73 GHz and f<sub>t</sub> of 110 GHz}, Key = {4547745} } @article{4179619, Author = {Brown, A.S. and Nguyen, L.D. and Metzger, R.A. and Schmitz, A.E. and Henige, J.A.}, Title = {Growth and properties of high mobility strained inverted AlInAs-GaInAs modulation doped structures}, Journal = {J. Vac. Sci. Technol. B, Microelectron. Process. Phenom. (USA)}, Volume = {10}, Number = {2}, Pages = {1017 - 19}, Address = {Austin, TX, USA}, Year = {1992}, url = {http://dx.doi.org/10.1116/1.586402}, Keywords = {aluminium compounds;electron gas;electron mobility;gallium arsenide;high electron mobility transistors;III-V semiconductors;impurity scattering;indium compounds;surface segregation;}, Abstract = {GaInAs-AlInAs inverted modulation-doped structures exhibit degraded two-dimensional electron gas (2DEG) transport properties when grown under standard conditions. This results from the surface segregation of Si from the donor layer into the GaInAs channel layer. Consequently, the 2DEG has poor mobility due to increased ionized impurity scattering. The authors have obtained high mobility inverted structures through the inhibition of this surface segregation by growing the spacer layer at a greatly reduced substrate temperature. Inverted modulation doped structures optimized for high frequency device applications require the use of thin channel layers. In order to obtain a large charge density (>2.3×10<sup>12</sup> cm<sup>-2</sup>) with high quality transport characteristics, In-rich, strained channels are required. This paper presents the results of an investigation of the electronic and optical properties of strained, inverted, thin-channel modulation doped structures. Channel thicknesses of 50-200 Å and In compositions of 53% to 80% were investigated. A 300 K electron mobility of 13000 cm<sup>2</sup>/V s was obtained with a sheet charge density of 2.4×10<sup>12</sup> cm<sup>-2</sup> for a 75 Å thick Ga<sub>0.27</sub>In<sub>0.73</sub>As channel}, Key = {4179619} } @article{4107436, Author = {Brown, A.S. and Metzger, R.A. and Henige, J.A. and Nguyen, L. and Lui, M. and Wilson, R.G.}, Title = {Effect of Si movement on the electrical properties of inverted AlInAs-GaInAs modulation doped structures}, Journal = {Appl. Phys. Lett. (USA)}, Volume = {59}, Number = {27}, Pages = {3610 - 12}, Year = {1991}, url = {http://dx.doi.org/10.1063/1.106394}, Keywords = {aluminium compounds;carrier mobility;electron gas;gallium arsenide;Hall effect;III-V semiconductors;indium compounds;semiconductor junctions;silicon;surface segregation;}, Abstract = {Inverted modulation doped structures typically exhibit degraded electrical characteristics. For the AlInAs-GaInAs heterojunction system, the reduction in electron mobility for two-dimensional electron gases formed at inverted interfaces can be greater than 50% at 300 K as compared to those formed at normal interfaces. The authors' data show that the reduction in mobility is due to the movement of Si into the GaInAs channel. The Si movement is found to be dramatically reduced by growing the AlInAs spacer at the inverted interface at a substrate temperature of 300-350°C. Device structures have been grown using this technique which exhibit the highest conductivity obtained for any 2DEG system}, Key = {4107436} } @article{91080271574, Author = {Metzger, R.A. and Brown, A.S. and Stanchina, W.E. and Lui, M. and Wilson, R.G. and Kargodorian, T.V. and McCray, L.G. and Henige, J.A.}, Title = {Growth and characterization of low temperature AlInAs}, Journal = {Journal of Crytal Growth}, Volume = {111}, Number = {1-4}, Pages = {445 - 449}, Address = {La Jolla, CA, USA}, Year = {1991}, url = {http://dx.doi.org/10.1016/0022-0248(91)91017-5}, Keywords = {Molecular Beam Epitaxy;Photoluminescence;X-rays - Diffraction;Mass Spectrometry;Semiconducting Indium Phosphide;}, Abstract = {Al<sub>0.48</sub>In<sub>0.52</sub>As lattice matched to InP and grown by MBE over a temperature range of 250 to 100°C and under an As<sub>4</sub> pressure of 1 × 10<sup>-6</sup> to 2 × 10<sup>-5</sup> Torr has been investigated. Over this temperature range of 250 to 100°C, resistivity decreases from 2 × 10<sup>7</sup> to 3 × 10<sup>6</sup> Ω cm while photoluminescence intensity decreases by two orders of magnitude. Resistivity showed little sensitivity to change in As<sub>4</sub> overpressure over the range investigated. Single crystal samples grown in the range of 100 to 150°C showed nonstochiometric excess As of up to 1.4% as determined by secondary ion mass spectrometry, and lattice expansion of 0.1% as determined by X-ray diffraction. Samples grown at temperatures greater than 200°C showed no excess As or lattice expansion.}, Key = {91080271574} } @article{92020412149, Author = {Schmitz, A. E. and Nguyen, L. D. and Brown, A. S. and Metzger, R. A.}, Title = {InP-based inverted high electron mobility transistors}, Journal = {IEEE Transactions on Electron Devices}, Volume = {38}, Number = {12}, Pages = {2702 -}, Address = {Boulder, CO, USA}, Year = {1991}, url = {http://dx.doi.org/10.1109/16.158723}, Keywords = {Semiconducting Indium Phosphide;Semiconducting Aluminum Compounds;}, Abstract = {Summary form only given. The fabrication and characterization of an inverted high-electron-mobility transistor (HEMT) in the AlInAs/GaInAs-on-InP material system are reported. Inverted HEMTs, which have the donor layer beneath the channel, have the potential for higher transconductance, current gain cutoff frequency, and power gain cutoff frequency than conventional HEMTs because the gate can be placed closer to the two-dimensional electron gas (2DEG).}, Key = {92020412149} } @article{92010390276, Author = {Matloubian, M. and Nguyen, L. D. and Brown, A. S. and Larson, L. E. and Melendes, M. A. and Thompson, M. A.}, Title = {High power and high efficiency AlInAs/GaInAs on InP HEMTs}, Journal = {IEEE MTT-S International Microwave Symposium Digest}, Volume = {2}, Pages = {721 - 724}, Address = {Boston, MA, USA}, Year = {1991}, url = {http://dx.doi.org/10.1109/MWSYM.1991.147105}, Keywords = {Microwave Measurements;Amplifiers, Power Type;}, Abstract = {The authors report on the development of AlInAs/GaInAs-on-InP power HEMTs (high electron mobility transistors). Output power densities of more than 730 mW/mm and 960 mW/mm with power-added efficiencies (PAE) of 50% and 40%, respectively, were achieved at 12 GHz. When biased for maximum efficiency, a PAE of 59% and an output power of 470 mW/mm with 11.3 dB gain were obtained. These results demonstrate the viability of these HEMTs for power amplification. Considering that these HEMTs have an f<sub>max</sub> of over 200 GHz, they should also have good power performance at millimeter-wave frequencies.}, Key = {92010390276} } @article{92060514906, Author = {Brown, A.S. and Nguyen, L.D. and Metzger, R.A. and Matloubian, M. and Schrnitz, A.E. and Lui, M. and Wilson, R.G. and Henige, J.A.}, Title = {Reduced silicon movement in GaInAs/AlInAs HEMT structures with low temperature AlInAs spacers}, Journal = {Institute of Physics Conference Series}, Volume = {120}, Pages = {281 - 286}, Address = {Seattle, WA, USA}, Year = {1991}, Keywords = {Silicon and Alloys - Diffusion;Semiconducting Gallium Arsenide;Semiconducting Indium Compounds;Semiconducting Aluminum Compounds;Molecular Beam Epitaxy - Applications;}, Abstract = {High electron mobility transistors fabricated from GaInAs/AlInAs modulation-doped structure currently exhibit the highest current gain cut-off frequency, highest maximum frequency of oscillation and lowest noise figure of any three terminal device. The data presented show that the degraded characteristics of the inverted modulation-doped interface, as compared with the normal AlInAs on GaInAs, result from the segregation of silicon in AlInAs. The authors have reduced the magnitude of these deleterious effects by growing a thin layer of AlInAs immediately following the doped region at significantly reduced substrate temperatures. The degree of silicon segregation as a fucntion of substrate temperature is discussed.also}, Key = {92060514906} } @article{3947624, Author = {Brown, A.S.}, Title = {An overview of microwave waveguide technology}, Journal = {Electrotechnology (UK)}, Volume = {2}, Number = {3}, Pages = {120 - 2}, Year = {1991}, Keywords = {guided electromagnetic wave propagation;waveguides;}, Abstract = {With the increasing demand for microwave circuitry in both the consumer and industrial markets the engineering expertise to develop these techniques is becoming a key issue. The profusion of engineers now being faced with the problems of signal processing in the gigahertz frequency range is making a basic understanding of the principles an essential skill for all electronics engineers. Point to point digital radio, satellite TV, information systems, physiotherapy treatment and radar are just a few examples of this ever increasing application field. The author provides an insight into transmission principles in the SHF band and beyond. A lower limit of 3 GHz is assumed. The author considers waveguide propagation in the TE, TEM and TM modes. Construction practicalities, circular waveguides, health aspects and applications are discussed}, Key = {3947624} } @article{3846550, Author = {Brown, A.S. and Spackman, M.A.}, Title = {A model study of the κ-refinement procedure for fitting valence electron densities}, Journal = {Acta Crystallogr. A, Found. Crystallogr. (Denmark)}, Volume = {A47}, Pages = {21 - 9}, Year = {1991}, url = {http://dx.doi.org/10.1107/S0108767390009163}, Keywords = {HF calculations;X-ray crystallography calculation methods;}, Abstract = {Monopole electron-density deformations for first- and second-row atoms are obtained using Hirshfeld partitioning of near Hartree-Fock limit electron densities for 28 diatomics. The κ-refinement model [Coppens, Guru Row, Leung, Stevens, Becker and Yang, Acta Cryst. A35, 63-72 (1979)] is applied to these monopole deformations and its success in modelling them is gauged by means of deformation radial distribution plots, <i>r</i><sup>2</sup>Δρ(<i>r</i>), and κ and charge-transfer values. The κ-refinement procedure proves to be remarkably successful in modelling the monopole deformations in this work. This in large part explains the successful application of the κ-refinement model to X-ray diffraction data, where it is capable of yielding an excellent point-charge model of the electrostatic potential in molecules and crystals}, Key = {3846550} } @article{3757163, Author = {Brown, A.S.}, Title = {The effects and implications of ESD on semiconductor technology}, Journal = {Electrotechnology (UK)}, Volume = {1}, Number = {4}, Pages = {217 - 19}, Year = {1990}, Keywords = {electrostatic discharge;integrated circuit manufacture;integrated circuit technology;VLSI;}, Abstract = {Since the development and implementation of large scale and very large scale integration techniques (LSI and VLSI), manufacturers have become increasingly aware of the damaging and destructive properties of electrostatic discharge (ESD) on semiconductor materials. The author expresses the opinion that this phenomena has not been taken seriously until relatively recently, and although semiconductor manufacturers have observed the necessary precautions for many years the practice is only now diversifying into installation, assembly, servicing and repair operations. The generation of ESD and its damaging effects are described, and practical methods of protection are presented, including a check list of precautions that should be taken}, Key = {3757163} } @article{3802514, Author = {Mishra, U.K. and Brown, A.S. and Jelloian, L.M. and Thompson, M. and Rosenbaum, S.E. and Nguyen, L.D. and Solomon, P.M. and Kiehl, R. and Kwark, Y.H.}, Title = {Room temperature and cryogenic performance of self-aligned AlInAs-GaInAs HEMTs with 0.15 μm gate length}, Journal = {Proc. SPIE - Int. Soc. Opt. Eng. (USA)}, Volume = {1288}, Pages = {21 - 9}, Address = {San Diego, CA, USA}, Year = {1990}, Keywords = {aluminium compounds;gallium arsenide;high electron mobility transistors;III-V semiconductors;indium compounds;plasma deposition;solid-state microwave devices;}, Abstract = {A novel self-aligned technique for 0.15 μm gate length AlInAs-GaInAs HEMTs has been demonstrated. Devices with an oxide sidewall yielded an f<sub>T</sub> of 177 GHz whereas devices with no sidewall exhibited an f<sub>T</sub> greater than 250 GHz. The difference has been related to process damage during plasma deposition of SiO<sub>2</sub>. An extrinsic f<sub>T</sub> of 292 GHz was measured at 77 K}, Key = {3802514} } @article{94071327430, Author = {Delaney, M.J. and Brown, A.S. and Mishra, U.K. and Chou, C.S. and Larson, L.E. and Nguyen, L. and Jensen, J.}, Title = {Low temperature MBE growth of GaAs and AllnAs for high speed devices}, Pages = {189 - 194}, Address = {Karuizawa, Jpn}, Year = {1990}, Key = {94071327430} } @article{3695770, Author = {Mishra, U.K. and Brown, A.S. and Jensen, J.F.}, Title = {High performance AlInAs-GaInAs HEMTs and HBTs}, Journal = {Gallium Arsenide and Related Compounds 1989. Proceedings of the Sixteenth International Symposium}, Pages = {605 - 12}, Address = {Karuizawa, Japan}, Year = {1990}, Keywords = {aluminium compounds;gallium arsenide;heterojunction bipolar transistors;high electron mobility transistors;III-V semiconductors;indium compounds;semiconductor junctions;}, Abstract = {AlInAs-GaInAs HEMTs with f<sub>t</sub>>2000 GHz and minimum noise figure of 0.8 dB at 63.5 GHz have been fabricated. Ring oscillators with gate delay of 6 pS and static dividers with operating frequency of 26.7 GHz have been demonstrated. AlInAs-GaInAs HBTs with f<sub>T</sub> of 49 GHz, f<sub>max</sub> of 62 GHz have been achieved. The maximum operating frequency of static dividers was 15 GHz}, Key = {3695770} } @article{89095061495, Author = {Brown, A.S. and Mishra, U.K. and Rosenbaum, S.E.}, Title = {Effect of interface and alloy quality on the DC and RF performance of Ga0.47In0.53As-Al0.48In0.52As HEMT's.}, Journal = {IEEE Transactions on Electron Devices}, Volume = {36}, Number = {4 pt 1}, Pages = {641 - 645}, Year = {1989}, url = {http://dx.doi.org/10.1109/16.22468}, Keywords = {Electric Conductivity;Semiconducting Gallium Compounds;Semiconducting Aluminum Compounds;}, Abstract = {Ga<sub>0.47</sub>In<sub>0.53</sub>As-Al<sub>0.48</sub>In<sub>0.52</sub>As high-electron-mobility transistors (HEMTs) were fabricated in materials with varying degrees of alloy and interface disorder. The conductivities of the expitaxial layers are highest for material with the smallest amount of interface roughness and lowest for samples with poor-quality interfaces. The transconductances and unity current gain cutoff frequencies of the fabricated devices with 0.2-μm gates are similarly affected.}, Key = {89095061495} } @article{90056030370, Author = {Delaney, M.J. and Brown, A.S. and Mishra, U.K. and Chou, C.S. and Larson, L.E. and Nguyen, L. and Jensen, J.}, Title = {Low temperature MBE growth of GaAs and AlInAs for high speed devices}, Pages = {64 - 72}, Address = {Ithaca, NY, USA}, Year = {1989}, url = {http://dx.doi.org/10.1109/CORNEL.1989.79822}, Keywords = {Transistors, Field Effect--Fabrication;Molecular Beam Epitaxy;Semiconducting Gallium Arsenide--Growth;}, Abstract = {Low-temperature GaAs buffer technology was used to fabricate high-performance 0.2-μm-gate-length, spike-doped GaAs MESFETs. A 400.0-nm low-temperature GaAs buffer was grown by molecular beam epitaxy (MBE) at a substrate temperature of 300°C. The substrate temperature was raised to 580°C for a brief in situ anneal and followed by the growth of the active spike-doped GaAs MESFET structure. The peak extrinsic transconductance, g<sub>m</sub>, was 600 mS/mm with an average pinch-off voltage, V<sub>po</sub>, of -0.6 V. An output conductance, g<sub>o</sub>, of 24 mS/mm resulted in a voltage gain of 25. The extrapolated f<sub>T</sub> of the devices was 79 GHz. Static SCFL (source-coupled FET logic) frequency dividers fabricated in this technology exhibit a maximum clock rate of 22 GHz. Low-temperature AlInAs buffer growth has been applied to GaInAs/AlInAs HEMT (high-electron-mobility transistor devices on InP. A 250.0-nm AlInAs buffer was grown at a substrate temperature of 150°C, followed by an anneal under arsenic overpressure and a GaInAs/AlInAs superlattice prior to the HEMT structure, which is grown at T</sub> = 510°C. Devices fabricated with 0.2-μm gates had g<sub>m</sub> of 670 mS/mm and g<sub>o</sub> of 2.55 mS/mm, giving a voltage gain of 250.}, Key = {90056030370} } @article{3506085, Author = {Brown, A.S. and Mishra, U.K. and Larson, L.E. and Rosenbaum, S.E.}, Title = {The elimination of DC I-V anomalies in Ga0.47In0.53As-Al0.48In0.52As HEMTs}, Journal = {Gallium Arsenide and Related Compounds 1988. Proceedings of the Fifteenth International Symposium}, Pages = {445 - 8}, Address = {Atlanta, GA, USA}, Year = {1989}, Keywords = {aluminium compounds;gallium arsenide;high electron mobility transistors;III-V semiconductors;indium compounds;p-n heterojunctions;}, Abstract = {GaInAs-AlInAs HEMTs have improved DC and RF performance as compared with GaInAs-(AlGa)As HEMTs. The drain-source I-V characteristics exhibit a kink related to trap ionization in the AlInAs buffer. This kink is eliminated by using a GaInAs buffer. Sidegating is also dramatically reduced with the GaInAs buffer}, Key = {3506085} } @article{90120074434, Author = {Mishra, U.K. and Brown, A.S. and Jelloian, L.M. and Thompson, M. and Nguyen, L.D. and Rosenbaum, S.E.}, Title = {Novel high performance self-aligned 0.15 micron long T-gate AlInAs-GaInAs HEMTs}, Journal = {Technical Digest - International Electron Devices Meeting}, Pages = {101 - 104}, Address = {Washington, DC, USA}, Year = {1989}, url = {http://dx.doi.org/10.1109/IEDM.1989.74237}, Keywords = {Semiconducting Aluminum Compounds;Semiconducting Gallium Compounds;}, Abstract = {A novel self-aligned technique for 0.15-μm-gate-length HEMTs (high electron mobility transistors) has been demonstrated. This technology uses a 0.15-μm-long T-gate structure defined by e-beam lithography with a SiO<sub>2</sub> sidewall to implement the self-aligned scheme. The resultant device has low source and drain resistances, low gate resistance (200 Ω/mm), and a passivating layer over the active channel. Devices with an oxide sidewall yielded an f<sub>T</sub> of 177 GHz, whereas devices with no sidewall exhibited an f<sub>T</sub> greater than 250 GHz. The difference has been related to process damage during plasma deposition of SiO<sub>2</sub>.}, Key = {90120074434} } @article{90076090867, Author = {Brown, April S. and Chou, Chia S. and Delaney, Michael J. and Hooper, Catherine E. and Jensen, Joseph F. and Larson, Lawrence E. and Mishra, Umesh K. and Nguyen, Loi D. and Thompson, Mark S.}, Title = {Low-temperature buffer AlInAs/GaInAs on InP HEMT technology for ultra-high-speed integrated circuits}, Journal = {Technical Digest - GaAs IC Symposium (Gallium Arsenide Integrated Circuit)}, Pages = {143 - 146}, Address = {San Diego, CA, USA}, Year = {1989}, Keywords = {Logic Devices--Gates;Electronic Circuits, Flip Flop;Crystals--Epitaxial Growth;}, Abstract = {A report is presented on the development of a planar low-temperature buffer AlInAs/GaInAs on InP high-electron-mobility transistor (HEMT) technology for use in digital and analog integrated circuits. This technology is attractive for circuit applications because of the high achievable f<sub>T</sub> and f<sub>max</sub>, low output conductance and gate leakage current, and reduced susceptibility to backgating effects. Two alternative logic families--UFL and SCFL (source-coupled FET logic)--were chosen for the realization of digital circuits. Measurements on the UFL ring oscillators exhibited a minimum gate delay of 13 pS with a power dissipation of 1.1 mW/gate at room temperature. The gate delay rose to 25 pS when the power dissipation increased to 3 mW/gate. This gate delay is expected to drop significantly with reductions in diode level-shift series resistance and improvements in transistor f<sub>T</sub>. The most complex SCFL circuit tested was a divide-by-eight counter. The SCFL circuits were configured as flip-flops in the divide-by-eight mode. The circuit operated at a maximum clock rate of 12.5 GHz.}, Key = {90076090867} } @article{90025161317, Author = {Mishra, Umesh K. and Brown, April S. and Delaney, M.J. and Greiling, Paul T. and Krumm, Charles F.}, Title = {AlInAs-GaInAs HEMT for microwave and millimeter-wave applications}, Journal = {IEEE Transactions on Microwave Theory and Techniques}, Volume = {37}, Number = {9}, Pages = {1279 - 1285}, Year = {1989}, url = {http://dx.doi.org/10.1109/22.32210}, Keywords = {Semiconducting Indium Compounds--Applications;Microwave Devices;Semiconducting Aluminum Compounds--Applications;Amplifiers;}, Abstract = {The status of lattice-matched high-electron-mobility transistors (HEMTs) and pseudomorphic AlInAs-GaInAs grown on In substrates is reviewed. The best lattice-matched devices with 0.1-μm gate length had a transconductance g<sub>m</sub> = 1080 mS/mm and a unity current gain cutoff frequency f<sub>T</sub> = 178 GHz, whereas similar pseudomorphic HEMTs had g<sub>m</sub> = 1160 mS/mm and f<sub>T</sub> = 210 GHz. Single-stage V-band amplifiers demonstrated 1.3- and 1.5-dB noise figures and 9.5- and 8.0-dB associated gains for the lattice-matched and pseudomorphic HEMTs, respectively. The best performance achieved was a minimum noise figure of F<sub>min</sub> = 0.8 dB with a small-signal gain of G<sub>a</sub> = 8.7 dB.}, Key = {90025161317} } @article{90056020715, Author = {Mishra, U.K. and Brown, A.S. and Jelloian, L.M. and Melendes, M.A. and Thompson, M. and Rosenbaum, S.E. and Larson, L.E.}, Title = {Impact of buffer layer design on the performance of AlInAs-GaInAs HEMT's}, Journal = {IEEE Transactions on Electron Devices}, Volume = {36}, Number = {11 pt 1}, Pages = {2616 -}, Address = {Cambridge, MA, USA}, Year = {1989}, url = {http://dx.doi.org/10.1109/16.43731}, Keywords = {Electrons--Transport Properties;Semiconductor Materials--Doping;}, Abstract = {Summary form only given. The authors report a study of the impact of buffer layer design on the characteristics of Al<sub>0.48</sub>In<sub>0.52</sub>As-Ga<sub>0.47</sub>In<sub>0.53</sub>As HEMTs (high-electron-mobility transistors). The aim of the study is to understand and correct the problem of high output conductance observed in devices with a high transconductance. Devices with 1.0-μm gate lengths were fabricated using modulation-doped Al<sub>0.48</sub>In<sub>0.52</sub>As-Ga<sub>0.47</sub>In<sub>0.53</sub>As epitaxial layes which had sheet charge densities between 3 × 10<sup>12</sup> and 3.5 × 10<sup>12</sup> cm<sup>-2</sup> and mobilities at 300 K between 9000 and 10,000 cm</sup> V<sup>-1</sup> S<sup>-1</sup>. The different buffer layer designs used were: 1) a standard undoped Al<sub>0.48</sub>In<sub>0.52</sub>As buffer 250-nm-thick; 2) an Al<sub>0.48</sub>In<sub>0.52</sub>As buffer with a 20-angstrom thick highly doped p-type region 50 angstrom below the channel; 3) A Ga<sub>0.47</sub>In<sub>0.53</sub>As buffer with a 20-angstrom-thick highly doped p-type region below the channel; and 4) a low-temperature AlInAs buffer layer. The device with the low-temperature AlInAs had the best output characteristics, signifying that it was the best mode of confining electrons in the channel.}, Key = {90056020715} } @article{90046020788, Author = {Brown, April S. and Mishra, Umesh K. and Chou, C.S. and Hooper, C.E. and Melendes, M.A. and Thompson, M. and Larson, L.E. and Rosenbaum, S.E. and Delaney, M.J.}, Title = {AlInAs-GaInAs HEMT's utilizing low-temperature AlInAs buffers grown by MBE}, Journal = {IEEE Electron Device Letters}, Volume = {10}, Number = {12}, Pages = {565 - 567}, Year = {1989}, url = {http://dx.doi.org/10.1109/55.43141}, Keywords = {Semiconducting Aluminum Compounds;Crystals--Epitaxial Growth;Millimeter Waves;}, Abstract = {Low-temperature AlInAs buffer layers incorporated in AlInAs-GaInAs HEMT epitaxial layers grown by MBE are discussed. A growth temperature of 150°C followed by a short anneal is shown to eliminate kinks in the device I-V characteristic and sidegating and to reduce the output conductance dramatically.}, Key = {90046020788} } @article{89070310715, Author = {Jensen, Joseph F. and Mishra, Umesh K. and Brown, April S. and Salmon, Linton G. and Delaney, M.J.}, Title = {Ultrahigh speed static and dynamic frequency divider circuits}, Journal = {Microwave Journal}, Volume = {32}, Number = {3}, Pages = {10 -}, Year = {1989}, Keywords = {Electronic Equipment Manufacture;Electronic Equipment Testing;Transistors, Field Effect;Semiconducting Gallium Arsenide;Semiconducting Aluminum Compounds;}, Abstract = {This paper describes the design, fabrication and testing of high speed GaAs MESFET and AlInAs/GaInAs HEMT frequency divider circuits. GaAs MESFET static frequency dividers operate at frequencies up to 18 GHz, and GaAs MESFET dynamic dividers operate at frequencies up to 26.6 GHz. When the same static divide designs were implemented in AlInAs/GaInAs HEMT technology, the performance improved to frequencies up to 25.4 GHz. Electrooptic testing techniques were used to verify the performance of the GaAs MESFET dividers.}, Key = {89070310715} } @article{89125160265, Author = {Delaney, M.J. and Chou, C.S. and Larson, L.E. and Jensen, J.F. and Deakin, D.S. and Brown, A.S. and Hooper, W.W. and Thompson, M.A. and McCray, L.G. and Rosenbaum, S.E.}, Title = {GaAs MESFET digital integrated circuits fabricated with low temperature buffer technology}, Journal = {Proceedings of the Custom Integrated Circuits Conference}, Pages = {18 - 3}, Address = {San Diego, CA, USA}, Year = {1989}, url = {http://dx.doi.org/10.1109/CICC.1989.56782}, Keywords = {Semiconducting Gallium Arsenide;Transistors, Field Effect;Electronic Circuits, Frequency Dividing;}, Abstract = {High-performance digital integrated circuits have been fabricated with low-temperature buffer GaAs MESFET technology. The materials structure eliminates side-gating and light sensitivity, and improves FET performance. Individual transistors with a 0.2-μm gate length have a g<sub>m</sub> of 600 mS/mm and an extrapolated f<sub>T</sub> of 80 GHz. Static SCFL frequency dividers fabricated in this technology exhibit a maximum clock rate of 22 GHz.}, Key = {89125160265} } @article{90015161235, Author = {Delaney, M.J. and Chou, C.S. and Larson, Lawrence E. and Jensen, Joseph F. and Deakin, D.S. and Brown, April S. and Hooper, William W. and Thompson, M.A. and McCray, L.G. and Rosenbaum, Steven E.}, Title = {Low-temperature buffer GaAs MESFET technology for high-speed integrated circuit applications}, Journal = {IEEE Electron Device Letters}, Volume = {10}, Number = {8}, Pages = {355 - 357}, Year = {1989}, url = {http://dx.doi.org/10.1109/55.31755}, Keywords = {Transistors, Field Effect;Semiconducting Gallium Arsenide;Logic Devices;}, Abstract = {The fabrication of high-performance digital integrated circuits with low-temperature buffer (LTB) GaAs MESFET technology is presented. Individual 0.2-μm-gate-length transistors show a g<sub>m</sub> of 600 mS/mm and an extrapolated f<sub>T</sub> of 80 GHz. Backgating and light sensitivity are eliminated with the LTB technology. Static source-coupled FET logic frequency dividers exhibit a maximum clock rate of 22 GHz.}, Key = {90015161235} } @article{90035240892, Author = {Mishra, Umesh K. and Jensen, Joseph F. and Rensch, D.B. and Brown, April S. and Stanchina, William E. and Trew, Robert J. and Pierce, M.W. and Kargodorian, Tsolag V.}, Title = {Self-aligned AlInAs-GaInAs heterojunction bipolar transistors and circuits}, Journal = {IEEE Electron Device Letters}, Volume = {10}, Number = {10}, Pages = {467 - 469}, Year = {1989}, url = {http://dx.doi.org/10.1109/55.43102}, Keywords = {Semiconducting Aluminum Compounds;Semiconducting Gallium Compounds;Integrated Circuits;Electronic Circuits, Flip Flop;Electronic Circuits, Frequency Dividing;}, Abstract = {AlInAs-GaInAs heterojunction bipolar transistors (HBTs) and static flip-flop frequency dividers have been fabricated. An f<sub>t</sub> and an f<sub>max</sub> of 49 and 62 GHz, respectively, have been achieved in a device with a 2 x 5-μm<sup>2</sup> emitter. Current-mode logic (CML) was used to implement static divide-by-two and divide-by-four circuits. The divide-by-two circuit operated at 15 GHz with 82-mW power dissipation for the single flip-flop. The divide-by-four circuit operated at 14.5 GHz with a total chip power dissipation of 444 mW.}, Key = {90035240892} } @article{3403466, Author = {Jensen, J.F. and Mishra, U.K. and Brown, A.S. and Salmon, L.G. and Delaney, M.J.}, Title = {Ultrahigh speed static and dynamic frequency divider circuits}, Journal = {Microw. J. (USA)}, Volume = {32}, Number = {3}, Pages = {131 - 2}, Year = {1989}, Keywords = {aluminium compounds;field effect integrated circuits;frequency dividers;gallium arsenide;high electron mobility transistors;III-V semiconductors;indium compounds;integrated logic circuits;MMIC;Schottky gate field effect transistors;}, Abstract = {The authors describe the design, fabrication and testing of high speed GaAs MESFET and AlInAs-GaInAs HEMT frequency divider circuits. GaAs MESFET static frequency dividers operate at frequencies up to 18 GHz, and GaAs MESFET dynamic dividers operate at frequencies up to 26.6 GHz. When the same static divider designs were implemented in AlInAs-GaInAs HEMT technology, the performance improved to frequencies up to 25.4 GHz. Electro-optic testing techniques were used to verify the performance of the GaAs MESFET dividers}, Key = {3403466} } @article{3419258, Author = {Brown, A.S. and Delaney, M.J. and Singh, J.}, Title = {The effect of inhibited growth kinetics on GaInAs and AlInAs alloy and interface quality}, Journal = {J. Vac. Sci. Technol. B, Microelectron. Process. Phenom. (USA)}, Volume = {7}, Number = {2}, Pages = {384 - 7}, Address = {West Lafayette, IN, USA}, Year = {1989}, url = {http://dx.doi.org/10.1116/1.584756}, Keywords = {aluminium compounds;gallium arsenide;III-V semiconductors;indium compounds;molecular beam epitaxial growth;semiconductor epitaxial layers;semiconductor growth;}, Abstract = {Ga<sub>0.47</sub>In<sub>0.53</sub>As and Al<sub>0.48</sub>In<sub>0.52</sub>As alloys, lattice matched to InP substrates, are typically grown under conditions (low substrate temperature and high V/III flux ratios) which limit cation surface mobilities. For the (Al,Ga)As system, the growth of material with low-defect density and good microscopic surface morphology is dependent on highly mobile cations which can reach kink sites on the growing surface. In the (Al,In,Ga)As system, other factors such as the miscibility gap in the AlInAs phase diagram and the volatility of InAs component dominate the growth condition requirements. In order to determine the role kinetic limitations play in reducing the quality of GaInAs and AlInAs under `normal' molecular beam epitaxy growth conditions, epitaxial layers were grown at extremely low substrate temperatures and high V/III ratios to examine the sensitivity of materials properties to these growth conditions}, Key = {3419258} } @article{3329494, Author = {Yu-Peng Hu and Petroff, P.M. and Xueyu Qian and Brown, A.S.}, Title = {Substrate misorientation effects on the structure and electronic properties of GaInAs-AlInAs interfaces}, Journal = {Appl. Phys. Lett. (USA)}, Volume = {53}, Number = {22}, Pages = {2194 - 6}, Year = {1988}, url = {http://dx.doi.org/10.1063/1.100280}, Keywords = {aluminium compounds;cathodoluminescence;gallium arsenide;III-V semiconductors;indium compounds;luminescence of inorganic solids;molecular beam epitaxial growth;semiconductor quantum wells;}, Abstract = {The effects of substrate misorientation on the interface quality of Ga<sub>0.47</sub>In<sub>0.53</sub>As/Al<sub>048</sub>In<sub>0.52</sub>As quantum well structures grown by molecular beam epitaxy lattice matched on InP substrates have been investigated. Transmission electron microscopy and low-temperature (15 K) cathodoluminescence spectra have been used to characterize the GaInAs/AlInAs layers and analyze the effects of nucleation and growth kinetics on the heterojunction interface quality. The quantum well luminescence line shape correlates with the presence of compositional fluctuations in the AlInAs layers and thickness variations of the quantum wells for structures deposited on misoriented substrates. Rapid thermal annealing of these samples improves the quantum well luminescence characteristics}, Key = {3329494} } @article{3292053, Author = {Brown, A.S. and Mishra, U.K. and Henige, J.A. and Delaney, M.J.}, Title = {The effect of InP substrate misorientation on GaInAs-AlInAs interface and alloy quality}, Journal = {J. Appl. Phys. (USA)}, Volume = {64}, Number = {7}, Pages = {3476 - 80}, Year = {1988}, url = {http://dx.doi.org/10.1063/1.341482}, Keywords = {aluminium compounds;gallium arsenide;III-V semiconductors;indium compounds;luminescence of inorganic solids;photoluminescence;semiconductor epitaxial layers;semiconductor quantum wells;}, Abstract = {The quality of GaInAs-AlInAs epitaxial layers is found to be critically dependent on the degree of (100)-InP substrate misorientation. The alloy quality of both materials is improved when the substrate is misoriented 4° off the (100). The heterojunction interface quality as determined by the full width at half-maximum of quantum-well photoluminescence is also improved when a substrate misoriented by 4° is used. A degradation of both alloy and interface quality as compared to material on (100) InP is observed when the misorientation is 2°. These effects are also observed for strained quantum-well structures}, Key = {3292053} } @article{89034180723, Author = {Mishra, Umesh K. and Jensen, Joseph F. and Brown, April S. and Thompson, M.A. and Jelloian, L.M. and Beaubien, Randall S.}, Title = {Ultra-high-speed digital circuit performance in 0.2-μm gate-length AlInAs/GaInAs HEMT technology.}, Journal = {IEEE Electron Device Letters}, Volume = {9}, Number = {9}, Pages = {482 - 484}, Year = {1988}, url = {http://dx.doi.org/10.1109/55.6952}, Keywords = {LOGIC CIRCUITS;MICROWAVE DEVICES;}, Abstract = {The fabrication of fifteen-stage ring oscillators and static flip-flop frequency dividers with 0.2-μm gate-length AlInAs/GaInAs HEMT technology is described. The fabricated HEMT devices within the circuits demonstrated a g<sub>m</sub> transconductance of 750 mS/mm and a full-channel current of 850 mA/mm. The measured cutoff frequency of the device is 120 GHz. The shortest gate delay measured for buffered-FET-logic (BFL) ring oscillators at 300 K was 9.3 ps at 66.7 mW/gate (fan-out = 1); fan-out sensitivity was 1.5 ps per fanout. The shortest gate delay measured for capacitively enhanced logic (CEL) ring oscillaltors at 300 K was 6.0 ps at 23.8 mW/gate (fan-out = 1) with a fan-out sensitivity of 2.7 ps per fan-out. The CEL gate delay reduced to less than 5.0 ps with 11.35-mW power dissipation when measured at 77 K. The highest operating frequency for the static dividers was 26.7 GHz at 73.1 mW and 300 K.}, Key = {89034180723} } @article{89075010800, Author = {Mishra, U.K. and Brown, A.S. and Rosenbaum, S.E. and Delaney, M.J. and Vaughn, S. and White, K.}, Title = {Noise performance of submicrometer AlInAs-GaInAs HEMT's}, Journal = {IEEE Transactions on Electron Devices}, Volume = {35}, Number = {12}, Pages = {2441 -}, Year = {1988}, url = {http://dx.doi.org/10.1109/16.8861}, Keywords = {Semiconducting Aluminum Compounds;Semiconducting Gallium Compounds;Millimeter Waves;}, Abstract = {Record DC and RF performance of AlInAs-GaInAs lattice matched to InP HEMTs (high-electron-mobility transistors) with nominally 0.2- and 0.1-μm gate lengths have been achieved. The devices were fabricated on material grown by MBE (molecular-beam epitaxy) on Fe-doped InP substrates. The epitaxial layers consisted of an undoped AlInAs spacer, a highly doped AlInAs donor layer, an undoped Schottky-enhancing AlInAs layer, and, finally, a highly doped GaInAs layer contact layer. 50-μm-wide devices with 0.2- and 0.1-μm-long T-gates were fabricated. The 0.2-μm gate-length devices were tested at V-band. The single-state amplifier (waveguide to waveguide with no correction) exhibited a minimum noise figure F<sub>min</sub> of 1.8 dB with an associated gain 7.5 dB at 63.0 GHz. This translates to an amplifier noise measure of 2.10 dB. The corresponding device performance was a minimum noise figure of 1.4 dB with an associated gain of 8.5 dB. This corresponds to a device noise measure of 1.6 dB.}, Key = {89075010800} } @article{89054230190, Author = {Mishra, Umesh K. and Brown, April S.}, Title = {InGaAs/AlInAs HEMT technology for millimeter wave applications}, Journal = {Technical Digest - GaAs IC Symposium (Gallium Arsenide Integrated Circuit)}, Pages = {97 - 100}, Address = {Nashville, TN, USA}, Year = {1988}, url = {http://dx.doi.org/10.1109/GAAS.1988.11032}, Keywords = {Semiconducting Gallium Compounds;Molecular Beam Epitaxy;Transistors;Integrated Circuits;Millimeter Waves;}, Abstract = {AlInAS-GaInAs modulation-doped structures grown by MBE (molecular-beam epitaxy) on InP have demonstrated excellent electronic and optical properties. Extremely high sheet charge densities (n<sub>s</sub> ~5 × 10<sup>18</sup> cm<sup>-3</sup>) and room temperature mobilities (μ ~9500 cm<sup>2</sup> V<sup>-1</sup> s<sup>-1</sup>) have been achieved. 0.1-m-gate-length HEMTs (high-electron-mobility transistors) have exhibited an f<sub>t</sub> (unity current gain cutoff frequency) ~170 GHz, whereas single stage amplifiers using 0.2-μm-gate HEMTs have demonstrated a minimum noise figure of 0.8 dB and an associated gain of 8.7 dB. Ring oscillators have demonstrated 6-ps switching speeds and static frequency dividers operated at 26.7 GHz at room temperature.}, Key = {89054230190} } @article{89034180573, Author = {Jensen, Joseph F. and Mishra, U.K. and Brown, A.S. and Beaubien, R.S. and Thompson, M.A. and Jelloian, L.M.}, Title = {25 GHz static frequency dividers in AlInAs-GaInAs HEMT technology.}, Journal = {Digest of Technical Papers - IEEE International Solid-State Circuits Conference}, Volume = {31}, Pages = {268 - 269}, Address = {San Francisco, CA, USA}, Year = {1988}, Keywords = {SEMICONDUCTING ALUMINUM COMPOUNDS;LOGIC CIRCUITS;}, Abstract = {The authors describe the ultrahigh-speed performance of static flip-flop divide-by-two circuits implemented in both buffered FET logic (BFL) and capacitively enhanced logic (CEL) families utilizing 0.2-μm gate-length Al<sub>.48</sub>In<sub>.52</sub>As-Ga<sub>.4 7</sub>In<sub>.53</sub>As high-electron-mobility transistors (HEMT) fabricated on InP substrates. The dividers were tested on-wafer using a probe station at 300°K temperature. The highest operating frequency at 25.4 GHz was achieved with a CEL divider. At this frequency the divider dissipated 63.8 mW. A BFL divider operated at 25.2 GHz with 450 mW power dissipation.}, Key = {89034180573} } @article{89095050186, Author = {Mishra, U.K. and Brown, A.S. and Rosenbaum, S.E.}, Title = {DC and RF performance of 0.1 μm gate length Al.48In.52As-Ga.38In.62As pseudomorphic HEMT's}, Journal = {Technical Digest - International Electron Devices Meeting}, Pages = {180 - 183}, Address = {San Francisco, CA, USA}, Year = {1988}, url = {http://dx.doi.org/10.1109/IEDM.1988.32784}, Keywords = {Semiconducting Aluminum Compounds;}, Abstract = {The authors report on the epitaxial layer design, device fabrication, and millimeter-wave performance of lattice-matched and pseudomorphic AlInAs-GaInAs HEMTs (high-electron-mobility transistors). The authors fabricated 0.1-μm gate length HEMTs using pseudomorphic Al<sub>0.48</sub>In<sub>0.52</sub>As-Ga<sub>0.38</sub>In<sub>0.62</sub>As modulation-doped epitaxial layers and compared them with lattice-matched Al<sub>0.48</sub>In<sub>0.52</sub>As-Ga<sub>0.47</sub>In<sub>0.53</sub>As HEMTs. The pseudomorphic HEMTs demonstrated an external f<sub>T</sub> (current-gain cutoff frequency) of 205 GHz, which is the first demonstration of a transistor with an f<sub>T</sub> gt; 200 GHz. The V-band noise figure of an amplifier built with the lattice-matched, pseudomorphic HEMTs was 1.3 dB and 1.5 dB, respectively. The associated gain was 9.5 dB and 8.0 dB, respectively.}, Key = {89095050186} } @article{88070099662, Author = {Mishra, Umesh K. and Brown, A. S. and Jelloian, L. M. and Hackett, L. H. and Delaney, M. J.}, Title = {HIGH-PERFORMANCE SUBMICROMETER ALINAS-GAINAS HEMT'S.}, Journal = {IEEE Electron Device Letters}, Volume = {9}, Number = {1}, Pages = {41 - 43}, Year = {1988}, url = {http://dx.doi.org/10.1109/55.20407}, Keywords = {SEMICONDUCTING GALLIUM ARSENIDE;SEMICONDUCTING ALUMINUM COMPOUNDS;SEMICONDUCTING INDIUM COMPOUNDS;}, Abstract = {The performance of long (1. 3- mu m) and short (0. 3- mu m) gate-length Al//0//. //4//8In//0//. //5//2 As-Ga//0//. //4//7In//0//. //5//3 high-electron-mobility transistors (HEMTs) is reported. Transconductances of 465 and 650 mS/mm, respectively, were achieved. The 0. 3- mu m-long gate-length device exhibited an f//t greater than 80 GHz. These results are attributed to the excellent electronic properties of the AlInAs-GaInAs modulation-doped system.}, Key = {88070099662} } @article{89095050346, Author = {Mishra, U.K. and Jensen, J.F. and Rensch, D.B. and Brown, A.S. and Pierce, M.W. and McCray, L.G. and Kargodorian, T.V. and Hoefer, W.S. and Kastris, R.E.}, Title = {48 GHz AlInAs/GaInAs heterojunction bipolar transistors}, Journal = {Technical Digest - International Electron Devices Meeting}, Pages = {873 - 875}, Address = {San Francisco, CA, USA}, Year = {1988}, url = {http://dx.doi.org/10.1109/IEDM.1988.32948}, Keywords = {Semiconducting Aluminum Compounds;Semiconducting Gallium Compounds;Band Structure;Molecular Beam Epitaxy;Microwave Measurements;}, Abstract = {The authors report on the DC and RF performance of self-aligned Al<sub>0.48</sub>In<sub>0.52</sub>As-Ga<sub>0.47</sub>In<sub>0.53</sub>As heterojunction bipolar transistors. The properties that make the AlInAns/GalnAs material system extremely attractive for heterojunction bipolar transistors are discussed. The epitaxial layer structure was grown by molecular beam epitaxy on semi-insulating InP. The device structure is shown in cross section. A large variety of heterojunction bipolar transistor devices with different emitter sizes and with different numbers of emitter fingers have been fabricated. The common emitter characteristics of a single 5-μm × 5-μm emitter are reported.}, Key = {89095050346} } @article{89054230617, Author = {Mishra, Umesh K. and Brown, April S. and Rosenbaum, S.E. and Hooper, C.E. and Pierce, M.W. and Delaney, M.J. and Vaughn, S. and White, K.}, Title = {Microwave performance of AlInAs-GaInAs HEMT's with 0.2- and 0.1-μm gate length}, Journal = {IEEE Electron Device Letters}, Volume = {9}, Number = {12}, Pages = {647 - 649}, Year = {1988}, url = {http://dx.doi.org/10.1109/55.20424}, Keywords = {Molecular Beam Epitaxy;Semiconducting Indium Compounds;Amplifiers;}, Abstract = {The millimeter-wave performance is reported for Al<sub>0.48</sub>In<sub>0.52</sub>As-Ga<sub>0.47</sub>In<sub>0.53</sub>As high-electron-mobility transistors (HEMTs) with 0.2-μm and 0.1-μm-long gates on material grown by molecular-beam epitaxy on semi-insulating InP substrates. Devices of 50-μm width exhibited extrinsic transconductances of 800 and 1080 mS/mm, respectively. External f<sub>T</sub> (maximum frequency of oscillation) of 120 and 135 GHz, respectively, were measured. A maximum f<sub>T</sub> of 170 GHz was obtained from a 0.1 × 200-μm<sup>2</sup> device. A minimum noise figure of 0.8 dB and associated gain of 8.7 dB were obtained from a single-stage amplifier at frequencies near 63 GHz.}, Key = {89054230617} } @article{3158819, Author = {Brown, A.S. and Henige, J.A. and Delaney, M.J.}, Title = {Photoluminescence broadening mechanisms in high quality GaInAs-AlInAs quantum well structures}, Journal = {Appl. Phys. Lett. (USA)}, Volume = {52}, Number = {14}, Pages = {1142 - 3}, Year = {1988}, url = {http://dx.doi.org/10.1063/1.99185}, Keywords = {aluminium compounds;gallium arsenide;III-V semiconductors;indium compounds;luminescence of inorganic solids;photoluminescence;semiconductor superlattices;}, Abstract = {GaInAs-AlInAs quantum well structures have been analyzed by low-temperature photoluminescence. The photoluminescence linewidth (full width at half-maximum) of thicker quantum wells (>10 nm) grown directly on AlInAs buffer layers shows that an inverse relationship exists between interface quality and AlInAs alloy quality in agreement with the theoretical analysis of J. Singh, S. Dudley, B. Davies, and K.K. Bajaj [J. Appl. Phys. <b>60</b>, 3167 (1986)]. Thinner wells show much improved luminescence properties due to a growth of previous wells}, Key = {3158819} } @article{3189252, Author = {Brown, A.S. and Mishra, U.K. and Henige, J.A. and Delaney, M.J.}, Title = {The impact of epitaxial layer design and quality on GaInAs/AlInAs high-electron-mobility transistor performance}, Journal = {J. Vac. Sci. Technol. B, Microelectron. Process. Phenom. (USA)}, Volume = {6}, Number = {2}, Pages = {678 - 81}, Address = {Los Angeles, CA, USA}, Year = {1988}, url = {http://dx.doi.org/10.1116/1.584389}, Keywords = {aluminium compounds;gallium arsenide;high electron mobility transistors;III-V semiconductors;indium compounds;semiconductor epitaxial layers;}, Abstract = {Ga<sub>0.47</sub>In<sub>0.53</sub>As-Al<sub>0.48</sub>In<sub>0.52</sub>As high-electron-mobility transistors (HEMT's) exhibit high transconductance and gain because of the high conductivities achievable in the structures. The effect of epitaxial layer design (spacer thickness and active channel thickness) on conductivity is examined. Device characteristics are examined as a function of active channel thickness. Reduced output conductance is observed for a 200 Å channel, but with a reduced transconductance}, Key = {3189252} } @article{3287288, Author = {Jensen, J.F. and Mishra, U.K. and Brown, A.S. and Beuabien, R.S. and Thompson, M.A. and Jelloian, L.M.}, Title = {25 GHz static frequency dividers in AlInAs-GaInAs HEMT technology}, Journal = {1988 IEEE International Solid-State Circuits Conference. Digest of Technical Papers. 31st ISSCC. First Edition}, Pages = {268 - 9}, Address = {San Francisco, CA, USA}, Year = {1988}, Keywords = {aluminium compounds;field effect integrated circuits;flip-flops;frequency convertors;gallium arsenide;high electron mobility transistors;III-V semiconductors;indium compounds;integrated logic circuits;}, Abstract = {The authors describe the ultrahigh-speed performance of static flip-flop divide-by-two circuits implemented in both buffered FET logic (BFL) and capacitatively enhanced logic (CEL) families utilizing 0.2-μm gate-length Al<sub>0.48</sub>In<sub>0.52</sub>As-Ga<sub>0.47</sub>In<sub>0.53</sub>As high-electron-mobility transistors (HEMT) fabricated on InP substrates. The dividers were tested on-wafer using a probe station at 300 K temperature. The highest operating frequency at 25.4 GHz was achieved with a CEL divider. At this frequency the divider dissipated 63.8 mW. A BFL divider operated at 25.2 GHz with 450 mW power dissipation}, Key = {3287288} } @article{3132929, Author = {Mishra, U.K. and Brown, A.S. and Jelloian, L.M. and Hackett, L.H. and Delaney, M.J.}, Title = {High performance submicrometer AlInAs-GaInAs HEMTs}, Journal = {IEEE Trans. Electron Devices (USA)}, Volume = {ED-34}, Number = {11}, Pages = {2358 -}, Address = {Santa Barbara, CA, USA}, Year = {1987}, Keywords = {aluminium compounds;gallium arsenide;high electron mobility transistors;III-V semiconductors;indium compounds;molecular beam epitaxial growth;semiconductor epitaxial layers;}, Abstract = {The performance of long-gate and short-gate Al<sub>0.48</sub>In<sub>0.52</sub>As-Ga<sub>0.47</sub>In<sub>0.53</sub>As HEMTs fabricated in high-quality MBE (molecular-beam-epitaxially)-grown material is discussed. The device structures were grown lattice-matched to semi-insulating InP substrates. The typical layer consists of an AlInAs buffer, followed by an undoped GaInAs channel, a thin undoped AlInAs space, a doped AlInAs donor layer, an undoped AlInAs barrier layer, followed finally by an n<sup>+</sup> GaInAs cap layer. The two epitaxial layer designs (wafers <i>A</i> and <i>B</i>) investigated to date differed only in the GaInAs channel thickness, 80 nm for wafer <i>A</i> and 40 nm for wafer <i>B</i>. Both the wafers exhibited sheet charge density <i>n</i><sub>s</sub> and mobility values of approximately 3.5×10<sup>12</sup> cm<sup>-2</sup> and 9500 cm<sup>2</sup> V<sup>-1</sup> S<sup>-1</sup> at 300 K and 3×10<sup>12</sup> cm<sup>-2</sup> and 30000 cm<sup>2</sup> V<sup>-1</sup> S<sup>-1</sup> at 77 K. Devices with 1.3-μm gate length were fabricated on both wafers. Transconductances of over 465 mS/mm at 300 K were measured on several devices on both wafers}, Key = {3132929} } @article{87050067453, Author = {Palmateer, L. F. and Tasker, P. J. and Itoh, T. and Brown, A. S. and Wicks, G. W. and Eastman, L. F.}, Title = {MICROWAVE CHARACTERISATION OF 1 mu m-GATE Al//0//. //4//8In//0//. //5//2As/Ga//0//. //4//7 In//0//. //5//3As/InP MODFETs.}, Journal = {Electronics Letters}, Volume = {23}, Number = {1}, Pages = {53 - 55}, Year = {1987}, Keywords = {MICROWAVE DEVICES;SEMICONDUCTING ALUMINUM COMPOUNDS - Applications;SEMICONDUCTING GALLIUM COMPOUNDS - Applications;SEMICONDUCTING INDIUM COMPOUNDS - Applications;}, Abstract = {We report microwave characterisation of nominally 1 mu m-gate Al//0//. //4//8In//0//. //5//2As/Ga//0//. //4//7 In//0//. //5//3As (lattice-matched to InP) modulation-doped field-effect transistors (MODFETs). The Al//0//. //4//8In//0//. //5//2As/Ga//0//. //4//7 In//0//. //5//3As MODFETs have room-temperature extrinsic transconductances as high as 250mS/mm. A room-temperature unity-current-gain cutoff frequency (f//T) of 22 GHz and an f//m//a//x of 35 GHz were measured for a 1. 2 mu m-gate MODFET.}, Key = {87050067453} } @article{3157433, Author = {Mishra, U.K. and Jensen, J.F. and Brown, A.S. and Beaubien, R.S. and Jelloian, L.M.}, Title = {Ultra-high speed AlInAs-GaInAs HEMT technology}, Journal = {1987 International Electron Devices Meeting, IEDM. Technical Digeset (Cat. No.87CH2515-5)}, Pages = {879 - 80}, Address = {Washington, DC, USA}, Year = {1987}, Keywords = {aluminium compounds;field effect integrated circuits;gallium arsenide;high electron mobility transistors;III-V semiconductors;indium compounds;}, Abstract = {The authors report on the ultrahigh-speed performance of 15-stage ring oscillators utilizing 0.2-μm gate length Al<sub>0.48</sub>In<sub>0.52</sub>As-Ga<sub>0.47</sub>In<sub>0.53</sub>As HEMTs (high-electron-mobility transistors) fabricated on InP substrates. The AlInAs-GaInAs modulation-doped system is extremely attractive for high-speed digital and analog applications. Fifteen-stage ring oscillators were fabricated using both buffered FET logic (BFL) and capacitively enhanced logic (CEL) schemes and their performance was measured at room temperature (300 K). The shortest gate delay measured for BFL was 9.26 ps (fanout=1) with 66.7 mW/gate power dissipation. The shortest CEL gate delay was 7.21 ps (fanout=1) at 24.5 mW. The measured fanout, sensitivities for BFL and CEL are 1.5 ps and 2.7 ps per fanout respectively. As expected, CEL gates are faster than BFL gates at low fanout, but CEL is more sensitive to fanout because its output is not buffered}, Key = {3157433} } @article{3157573, Author = {Mishra, U.K. and Beaubien, R.S. and Delaney, M.J. and Brown, A.S. and Hackett, L.H.}, Title = {Low noise 0.1-μm GaAs MESFETS by MBE}, Journal = {Proceedings IEEE/Cornell Conference on Advanced Concepts in High Speed Semiconductor Devices and Circuits (Cat. No.87CH2526-2)}, Pages = {177 - 89}, Address = {Ithaca, NY, USA}, Year = {1987}, Keywords = {III-V semiconductors;molecular beam epitaxial growth;Schottky gate field effect transistors;semiconductor epitaxial layers;}, Abstract = {Demonstrates that by applying proper scaling techniques, high-performance 0.1-μm-gate-length GaAs MESFETs can be routinely fabricated. The noise performance of these devices compares favorably with that of state-of-the-art HEMT structures. The performance is limited at the present time by the parasitic device elements, namely, the source resistance, gate resistance, drain resistance, and output conductance. It is clear that using T-gate structures and further optimization of the epitaxial profiles will address these issues in the future}, Key = {3157573} } @article{88040055373, Author = {Mishra, U. K. and Brown, A. S. and Jelloian, L. M. and Hackett, L. H. and Delaney, M. J.}, Title = {HIGH PERFORMANCE SUBMICROMETER ALINAS-GAINAS HEMT'S.}, Journal = {IEEE Transactions on Electron Devices}, Volume = {ED-34}, Number = {11}, Pages = {4 -}, Year = {1987}, Keywords = {SEMICONDUCTOR DEVICES, FIELD EFFECT - Fabrication;MOLECULAR BEAM EPITAXY - Applications;}, Abstract = {The performance of long-gate and short-gate Al//0//. //4//8In//0//. //5//2As-Ga//0//. //4//7In//0//. //5//3As HEMTs fabricated on high-quality MBE (molecular-beam-epitaxially)-grown material is discussed. The device structures were grown lattice-matched to semi-insulating InP substrates. The typical layer consisted of an AlInAs buffer, followed by an undoped GaInAs channel, a thin undoped AlInAs space, a doped AlInAs donor layer, an undoped AlInAs barrier layer, followed finally by an n** plus GaInAs cap layer. The two epitaxial layer designs (wafers A & B) investigated to date differed only in the GaInAs channel thickness, 80 nm for wafer A and 40 nm for wafer B. Devices with 1. 3- mu m gate length were fabricated on both wafers. Transconductances of over 465 mS/mm at 300 K were measured on several devices on both wafers. There was no strong correlation between the channel thickness and the I-V characteristics. Devices with approximately 0. 30- mu m gate length were fabricated on wafer A. They exhibited transconductances of over 650 mS/mm at room temperature. The maximum drain current density was approimately 600 mA/mm which is twice the current density obtainable from single heterojunction AlGaAs-GaAs devices. This predicts a high fan-out capability for AlInAs-GaInAs HEMTs.}, Key = {88040055373} } @article{88080117571, Author = {Mishra, U. K. and Beaubien, R. S. and Delaney, M. J. and Brown, A. S. and Hackett, L. H.}, Title = {LOW NOISE 0. 1- mu m GaAs MESFETS BY MBE.}, Pages = {177 - 189}, Address = {Ithaca, NY, USA}, Year = {1987}, Keywords = {SEMICONDUCTOR DEVICES, FIELD EFFECT - Noise;SEMICONDUCTING GALLIUM ARSENIDE - Applications;MOLECULAR BEAM EPITAXY - Applications;}, Abstract = {It is demonstrated that by applying proper scaling techniques, high-performance 0. 1- mu m-gate-length GaAs MESFETs can be routinely fabricated. The noise performance of these devices compares favorably with that of state-of-the-art HEMT structures. The performance is limited at the present time by the parasitic device elements, namely, the source resistance, gate resistance, drain resistance, and output conductance. It is clear that using T-gate structures and further optimization of the epitaxial profiles will address these issues in the future.}, Key = {88080117571} } @article{3011865, Author = {Griem, H.T. and Hsieh, K.H. and D'Haenens, I.J. and Delaney, M.J. and Henige, J.A. and Wicks, G.W. and Brown, A.S.}, Title = {Molecular-beam epitaxial growth and characterization of strained GaInAs/AlInAs and InAs/GaAs quantum well two-dimensional electron gas field-effect transistors}, Journal = {J. Vac. Sci. Technol. B, Microelectron. Process. Phenom. (USA)}, Volume = {5}, Number = {3}, Pages = {785 - 91}, Address = {Cambridge, MA, USA}, Year = {1987}, url = {http://dx.doi.org/10.1116/1.583751}, Keywords = {aluminium compounds;carrier mobility;gallium arsenide;high electron mobility transistors;III-V semiconductors;indium compounds;molecular beam epitaxial growth;semiconductor growth;semiconductor superlattices;}, Abstract = {Defect free strained layer epitaxy opens possibilities for further improvement on the quantum well two-dimensional electron gas (TEG) structures grown using the GaInAs/AlInAs on InP materials system. Increased freedom with composition allows for optimizing certain properties of the structure, such as, the conduction edge discontinuity which controls the maximum sheet concentration (<i>n</i><sub>s</sub>); and the electron effective mass which influences the speed of the structure. These enhancements can be made, respectively, by increasing the Al concentration in the AlInAs and/or by decreasing the Ga concentration in the GaInAs. The maximum amount of strain which can be incorporated into the unrelaxed material sets an upper limit on the compositional tolerances. The tolerances will be shown to be large for the AlInAs and the active TEG GaInAs region. The compositions are obtained using the intensity oscillations observed in the reflective high-energy electron diffraction (RHEED) specular beam during growth of GaAs, AlAs, and subsequently GaInAs and AlInAs on GaAs. X-ray rocking curves and photoluminescence (PL) are used to verify the calibrations for growths on InP. The dependency of the mobility on strain is shown. In As/GaAs superlattice quantum well TEG structures were grown and characterized. Exceptionally high Si doping levels roughly 20 times the maximum obtained with Al<sub>0.25</sub>Ga<sub>0.75</sub>As have been achieved with lattice matched AlInAs}, Key = {3011865} } @article{2860841, Author = {Brown, A.S. and Itoh, T. and Wicks, G. and Eastman, L.F.}, Title = {Si diffusion in GaInAs-AlInAs high-electron-mobility transistor structures}, Journal = {J. Appl. Phys. (USA)}, Volume = {60}, Number = {10}, Pages = {3495 - 8}, Year = {1986}, url = {http://dx.doi.org/10.1063/1.337600}, Keywords = {aluminium compounds;diffusion in solids;gallium arsenide;Hall effect;high electron mobility transistors;III-V semiconductors;indium compounds;secondary ion mass spectra;semiconductor doping;silicon;}, Abstract = {Secondary-ion-mass spectrometry, Hall-effect measurements, and DC <i>I</i>-<i>V</i> characteristics of 1-μm Ga<sub>0.47</sub>In<sub>0.53</sub>As-Al<sub>0.48</sub>In<sub>0.52</sub>As high-electron mobility transistor structures indicate that significant diffusion of Si can occur in these layers. The source of the Si is both the intentional Si used for modulation doping of the devices, and Si which is an unintentional impurity in the Fe-doped InP substrates on which the layer is grown. Preannealing and polishing the substrates can lessen the effect}, Key = {2860841} } @article{2729119, Author = {Itoh, T. and Brown, A.S. and Camnitz, L.H. and Wicks, G.W. and Berry, J.D. and Eastman, L.F.}, Title = {Depletion- and enhancement-mode Al0.48In0.52As/Ga0.47In0.53As modulation-doped field-effect transistors with a recessed gate structure}, Journal = {Gallium Arsenide and Related Compounds 1985. Proceedings of the Twelfth International Symposium}, Pages = {571 - 6}, Address = {Karuizawa, Japan}, Year = {1986}, Keywords = {aluminium compounds;gallium arsenide;high electron mobility transistors;III-V semiconductors;indium compounds;}, Abstract = {Depletion- and enhancement-mode Al<sub>0.48</sub>In<sub>0.52</sub>As/Ga<sub>0.47</sub>In<sub>0.53</sub>As modulation doped field effect transistors with 1 μm gate length have been successfully fabricated by employing a recessed gate structure and an undoped Al<sub>0.48</sub>In<sub>0.52</sub>As top layer beneath the gate metal. The fabricated devices exhibited good DC characteristics with a high transconductance and a complete pinch-off characteristic. For both depletion- and enhancement-mode devices, the transconductances of 250 mS/mm and 300 mS/mm have been measured at 300K and 77K, respectively}, Key = {2729119} } @article{87100161213, Author = {Griem, H. T. and Hsieh, K. H. and D'Haenens, I. J. and Delaney, M. J. and Henige, J. A. and Wicks, G. W. and Brown, A. S.}, Title = {CHARACTERIZATION OF STRAINED GaInAs/AlInAs QUANTUM WELL TEGFETS GROWN BY MOLECULAR BEAM EPITAXY.}, Journal = {Journal of Crystal Growth}, Volume = {81}, Number = {1-4}, Pages = {383 - 390}, Year = {1986}, url = {http://dx.doi.org/10.1016/0022-0248(87)90421-0}, Keywords = {MOLECULAR BEAM EPITAXY;SEMICONDUCTING GALLIUM COMPOUNDS;}, Abstract = {Defect free strained layer epitaxy opens possibilities for further improvement on the quantum well two-dimensional electron gas FET (TEGFET) structures grown using the GaInAs/AlInAs on InP materials system. Increased freedom with composition allows for optimizing certain properties of the structure, such as, the conduction edge discontinuity which controls the maximum sheet concentration (n//s); and the electron effective mass which influences the speed of the structure. These enhancements can be made, respectively, by increasing the Al concentration in the AlInAs and/or by decreasing the Ga concentration in the GaInAs. The maximum amount of strain which can be incorporated into the unrelaxed material sets an upper limit on the compositional tolerances. The tolerances are large for the AlInAs and the active TEG GaInAs region. The compositions are obtained using the intensity oscillations observed in the reflection high energy electron diffraction (RHEED) specular beam during growth of GaAs, AlAs, and subsequently GaInAs and AlInAs on GaAs. X-ray rocking curves and photoluminescence (PL) are used to verify the calibrations for growths on InP.}, Key = {87100161213} } @article{2933461, Author = {Mishra, U.K. and Beaubien, R.S. and Delaney, M.J. and Brown, A.S. and Hackett, L.H.}, Title = {MBE grown GaAs MESFETs with ultra-high gm and fT}, Journal = {International Electron Devices Meeting 1986. Technical Digest (Cat. No.86CH2381-2)}, Pages = {829 - 31}, Address = {Los Angeles, CA, USA}, Year = {1986}, Keywords = {gallium arsenide;III-V semiconductors;molecular beam epitaxial growth;Schottky gate field effect transistors;solid-state microwave devices;}, Abstract = {The authors report on the design, fabrication and test performance of GaAs MESFETs with 0.1-μm gate length. The devices were fabricated on epitaxial material grown by molecular beam epitaxy (MBE) on a Riber 2300 system. The main features of the design are discussed}, Key = {2933461} } @article{2716244, Author = {Brown, A.S. and Wicks, G.W. and Eastman, L.F.}, Title = {Mn redistribution in doped GaInAs}, Journal = {J. Vac. Sci. Technol. B, Microelectron. Process. Phenom. (USA)}, Volume = {4}, Number = {2}, Pages = {543 - 4}, Address = {Minneapolis, MN, USA}, Year = {1986}, url = {http://dx.doi.org/10.1116/1.583424}, Keywords = {electromigration;gallium arsenide;III-V semiconductors;impurity distribution;indium compounds;secondary ion mass spectra;semiconductor epitaxial layers;}, Abstract = {Summary for only given. The authors discuss some aspects of the diffusion behavior of Mn in the presence of electric fields. Impurity profiles were measured by using secondary ion mass spectrometry (SIMS). No matrix effects exist for Mn detection in either <i>p</i>- or <i>n</i>-type GaInAs, so the data were interpreted in a straightforward manner by comparison with ion-implanted standards}, Key = {2716244} } @article{85070089648, Author = {Brown, A. S. and Palmateer, S. C. and Wicks, G. W. and Eastman, L. F. and Calawa, A. R.}, Title = {BEHAVIOR OF UNINTENTIONAL IMPURITIES IN Ga//0//. //4//7In//0//. //5//3As GROWN BY MBE.}, Journal = {Journal of Electronic Materials}, Volume = {14}, Number = {3}, Pages = {367 - 378}, Year = {1985}, Keywords = {SEMICONDUCTOR MATERIALS - Impurities;MOLECULAR CRYSTALS - Epitaxial Growth;SEMICONDUCTING INDIUM COMPOUNDS - Charge Carriers;MOLECULAR BEAMS;}, Abstract = {A number of factors contribute to the high n-type background carrier concentration (high 10**1**5 to low 10**1**6 cm** minus **3) measured in MBE Ga//0//. //4//7In//0//. //5//3As lattice-matched to InP. The results of this study indicate that the outdiffusion of impurities from InP substrates into GaInAs epitaxial layers can account for as much as two-thirds of the background carrier concentration and can reduce mobilities by as much as 40%. These impurities and/or defects can be gettered at the surfaces of the InP by heat treatment and then removed by polishing. The GaInAs epitaxial layers grown on the heat-treated substrates have significantly improved electrical properties. Hall and SIMS measurements indicate that both donors and acceptors outdiffuse into the epitaxial layers during growth resulting in heavily compensated layers with reduced mobilities. The dominant donor species was idenfified by SIMS as Si, and the dominant acceptors as Fe, Cr and Mn.}, Key = {85070089648} } @article{2759081, Author = {Itoh, T. and Brown, A.S. and Camnitz, L.H. and Wicks, G.W. and Berry, J.D. and Eastman, L.F.}, Title = {A recessed gate Al0.48In0.52As/Ga0.47In0.53As modulation doped field effect transistor}, Journal = {Proceedings of the IEEE/Cornell Conference on Advanced Concepts in High Speed Semiconductor Devices and Circuits (Cat. No.85CH2173-3)}, Pages = {92 - 101}, Address = {Ithaca, NY, USA}, Year = {1985}, Keywords = {aluminium compounds;gallium arsenide;high electron mobility transistors;III-V semiconductors;indium compounds;}, Abstract = {1-μm gate Al<sub>0.48</sub>In<sub>0.52</sub>As/Ga<sub>0.47</sub>In<sub>0.53</sub>As modulation-doped field effect transistors have been successfully fabricated by using a recessed gate structure and an undoped Al<sub>0.48</sub>In<sub>0.52</sub>As top layer beneath the gate metal. The fabricated devices exhibited good DC characteristics with a high transconductance and a complete pinch-off characteristic. DC transconductances of 200 mS/mm and 265 mS/mm have been measured at 300K and 77K, respectively}, Key = {2759081} } @article{2576615, Author = {Brown, A.S. and Palmateer, S.C. and Wicks, G.W. and Eastman, L.F. and Calawa, A.R. and Hitzman, C.}, Title = {The heat treatment of Fe-doped InP substrates for the growth of higher purity Ga0.47In0.53As by MBE}, Journal = {Semi-Insulating III-V materials}, Pages = {36 - 40}, Address = {Kah-nee-ta, OR, USA}, Year = {1984}, Keywords = {carrier density;carrier mobility;gallium arsenide;Hall effect;heat treatment;III-V semiconductors;impurities;indium compounds;iron;molecular beam epitaxial growth;semiconductor epitaxial layers;semiconductor growth;substrates;}, Abstract = {Impurity outdiffusion, in particular Fe, Mn, and Cr, from Fe-doped InP into GaInAs epitaxial layers during molecular beam epitaxy growth can account for as much as two-thirds of the carrier concentration and can reduce electron mobilities by as much as 40%. By heating the InP before growth and then polishing to remove the impurities which have been gettered at the surface, epitaxial layers with unintentional carrier concentrations less sensitive to substrate temperature and higher mobilities can be obtained. Fe-doped InP has been annealed under pure H<sub>2</sub>, a 92% Ar-8% H<sub>2</sub> mixture, and a PH<sub>3</sub> ambient to relate the efficiency of impurity gettering to the ambient heating. Hall measurements show that the carrier mobilities in epitaxial layers grown on InP annealed in a pure H<sub>2</sub> ambient increase more than in those layers grown on InP heated in an Ar-H<sub>2</sub> mixture. This suggests that the formation of phosphorus vacancies aids the surface gettering of outdiffusing impurities}, Key = {2576615} } @article{85010008414, Author = {Brown, A. S. and Wicks, G. W. and Eastman, L. F. and Palmateer, S. C.}, Title = {DEPENDENCE OF ELECTRICAL CHARACTERISTICS OF MBE Ga//0//. //4//7In//0//. //5//3As PLANAR DOPED BARRIERS ON InP SUBSTRATES.}, Journal = {Journal of Vacuum Science & Technology B: Microelectronics Processing and Phenomena}, Volume = {2}, Number = {2}, Pages = {194 - 196}, Address = {Atlanta, GA, USA}, Year = {1983}, url = {http://dx.doi.org/10.1116/1.582777}, Keywords = {SEMICONDUCTING GALLIUM COMPOUNDS;SEMICONDUCTING INDIUM COMPOUNDS;HEAT TREATMENT;ELECTRIC PROPERTIES;}, Abstract = {The potential barrier height in planar-doped barrier structures is particularly sensitive to the concentration of background impurities present in the nominally undoped regions. MBE grown GaInAs lattice matched to InP typically has n-type background carrier concentrations in the 10**1**6 cm** minus **3 range. This high level can cause lowering of the barrier to near zero. By subjecting the InP substrates to a heat treatment process before growth in order to inhibit impurity outdiffusion higher purity GaInAs can be grown and planar-doped barrier devices with more reproducible characteristics are expected.}, Key = {85010008414} } | |
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