POINT-DEFECTS AND DIFFUSION MECHANISMS PERTINENT TO THE GA SUBLATTICE OF GAAS

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, V-Ga(3-) 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-) (CVGa3-) has been found to exhibit a temperature independence or even a small negative temperature dependence in that, when the temperature is lowered, Cv is either unchanged or even slightly increases. This C behavior is consistent with many outstanding experimental results.