Papers Published

1. Chen, C.H. and Tan, T.Y., On the validity of the amphoteric-defect model in gallium arsenide and a criterion for Fermi-level pinning by defects, Appl. Phys. A, Mater. Sci. Process. (Germany), vol. A61 no. 4 (1995), pp. 397 - 405 [s003390050219] .
   (last updated on 2007/04/10)

   Abstract:
   Using the theoretically calculated point-defect total-energy values of Baraff and Schlueter in GaAs, an amphoteric-defect model has been proposed by Walukiewicz to explain a large number of experimental results. The suggested amphoteric-defect system consists of two point-defect species capable of transforming into each other: the doubly negatively charged Ga vacancy V^2-_Ga and the triply positively charged defect complex (AS_Ga+V_As)³⁺, with As_Ga being the antisite defect of an As atom occupying a Ga site and V_As being an As vacancy. When present in sufficiently high concentrations, the amphoteric defect system V^2-_Ga/(As_Ga+V_As)³⁺ is supposed to be able to pin the GaAs Fermi level at approximately the E_v+0.6 eV level position, which requires that the net free energy of the V_Ga/(As_Ga+V_As) defect system to be minimum at the same Fermi-level position. We have carried out a quantitative study of the net energy of this defect system in accordance with the individual point-defect total-energy results of Baraff and Schlueter, and found that the minimum net defect-system-energy position is located at about the E_v+1.2 eV level position instead of the needed E_v+0.6 eV position. Therefore, the validity of the amphoteric-defect model is in doubt. We have proposed a simple criterion for determining the Fermi-level pinning position in the deeper part of the GaAs band gap due to two oppositely charged point-defect species, which should be useful in the future

   Keywords:
   band structure;binding energy;defect states;Fermi level;gallium arsenide;III-V semiconductors;interstitials;point defects;vacancies (crystal);