Atomistic mechanisms of dopant-induced multiple quantum well mixing and related phenomena

摘要

We discuss mechanisms of Ga self-diffusion and impurity diffusion in GaAs, and of layer mixing enhancement in GaAs/AlGaAs multiple quantum wells (MQWs). Ga self-diffusion and Ga-Al interdiffusion are governed by the triply negatively charged Ga vacancies, VGa3−, under intrinsic and n-doping conditions, and by doubly positively charged Ga self-interstitials, IGa2+, under heavy p-doping conditions. The mechanisms responsible for enhancing MQW mixing are the Fermi-level effect for the n-dopants Si and Te, and the combined effects of the Fermi-level and the dopant diffusion-induced nonequilibrium point defects for the p-dopants Zn and Be. For n-type GaAs the donor Si atoms diffuse primarily also via VGa3−. For p-type GaAs the interstitial-substitutional impurities Zn and Be diffuse via the kickout mechanism and induce a supersaturation and an undersaturation in the concentrations of IGa2+, respectively, under indiffusion and outdiffusion conditi