Point defects, diffusion mechanisms, and superlattice disordering in gallium arsenide-based materials

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Abstract
This article reviews recent progresses in our understanding of the mechanisms of Ga self-diffusion and impurity diffusion in GaAs, and of the disordering of GaAs/AlGaAs superlattices. Gallium self-diffusion and AI-Ga interdiffusion under intrinsic and n-doping conditions are governed by the triply negatively charged group 111 sublattice vacancies V 3- Ga, while under heavy p-doping conditions most likely by the doubly positively charged self-interstitial I 2+ Ga. The GaAslAIGaAs superlattice disordering enhancement observed under n-doping by Si or by Te is due to the Fermi-level effect that increases the V 3- Ga 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 Fermilevel, which increases the I 2+ Ga concentration, and the dopant in-diffusion or out-diffusion induced I 2+ Ga supersaturation or undersaturation. respectively. In consistency with the Ga self-diffusion mechanism in GaAs, diffusion of the Si donor atoms occupying Ga sites is primarily also governed by G 3- Ga, while Si acceptor atoms occupying As sites, which is 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 I 2+ Ga supersaturation and undersaturation. respectively, under the in-diffusion and out-conditision conditions.

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