Point defects and diffusion mechanisms pertinent to the Ga sublattice of GaAs

Abstract

For the Ga sublattice of GaAs, the recent understanding of the impurity and self-diffusion mechanisms and the nature of the point defects responsible are discussed. Analyses of doping enhanced AlAs GaAs superlattice disordering data and impurity diffusion data have led to the conclusion that, under thermal equilibrium and intrinsic conditions, the triply-negatively-charged Ga vacancy (( V Ga 3−) governs Ga self-diffusion and AlGa interdiffusion in As-rich crystals, while the doubly-positively-charged Ga self-interstitial ( I Ga 2+) dominates in Ga-rich crystals. When doped sufficiently, dominates in n-type crystals, while I Ga 2+ dominates in p-type crystals, irrespective of the crystal composition. The V Ga 3− species also contributes to the diffusion of the main donor species Si, while I Ga 2+ also governs the diffusion of the main acceptor species Zn and Be via the kick-out mechanism. The thermal equilibrium concentration of V Ga 3− ( C V Ga 3− ) has been found to exhibit a temperature independence or even a small negative temperature dependence in that, when the temperature is lowered, C V Ga 3− ; is either unchanged or even slightly increases. This C V Ga 3− behavior is consistent with many outstanding experimental results.