Point defects, diffusion mechanisms, and superlattice disordering in gallium arsenide-based materials
This article reviews recent progress in understanding of the mechanisms of Ga self-diffusion and impurity diffusion in GaAs and the disordering of GaAs/AlGaAs superlattices. Gallium self-diffusion and Al-Ga interdiffusion under intrinsic and n-doping conditions are governed by the triply negatively charged group III sublattice vacancies VGa3-, while under heavy p-doping conditions most likely by the doubly positively charged self-interstitial IGa2+. The GaAs/AlGaAs superlattice disordering enhancement observed under n-doping by Si or by Te is due to the Fermi-level effect that increases the VGa3- concentration, while the observable or not observable disordering enhancement under p-doping by Zn or by Be is due to the combined effects of the Fermi-level, which increases the IGa2+ concentration, and the dopant in-diffusion or out-diffusion induced IGa2+ supersaturation or undersaturation, respectively. Consistent with the Ga self-diffusion mechanism in GaAs, diffusion of Si donor atoms occupying Ga sites is primarily also governed by VGa3-, while Si acceptor atoms occupying As sites, which are a minority fraction of the total, diffuses via a negatively charged As sublattice point defect species. The interstitial-substitutional p-type dopants Zn and Be diffuse via the kick-out mechanism. Their diffusion induces an IGa2+ supersaturation and undersaturation, respectively, under in-diffusion and out-diffusion conditions.
Tan, TY; Goesele, U; Yu, S
Critical Reviews in Solid State and Materials Sciences
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