Abstract:
Recent work has shown that Bi incorporation increases during molecular beam epitaxy (MBE) when surface processes are kinetically limited through increased growth rate. Herein we explore how the structural and optical properties of GaAs 1−xBix films are modified when grown under conditions with varying degrees of kinetic limitations realized through growth temperature and growth rate changes. Within the typical window of MBE growth conditions for GaAs 1−xBix, we compare films with similar (∼3%) compositions grown under conditions of reduced kinetic limitations, i.e., relatively low gallium supersaturation achieved at higher temperatures (∼350 °C) and lower growth rates (∼0.5 μm/h), to those grown farther from equilibrium, specifically, higher supersaturation achieved at lower growth temperatures (∼290 °C) and higher growth rates (∼1.4 μm/h). Both the x-ray diffraction full width at half maximum of the omega-2theta scan and the 300 K photoluminescence intensity increase when samples are grown under less kinetically limited conditions. We interpret these findings in relation to the incorporation of Bi-related microstructural defects that are more readily formed during less kinetically limited growth. These defects lead to enhanced luminescence efficiency due to the spatial localization of carriers.