GA SELF-DIFFUSION IN GAAS

Evidence is summarized which indicates that the self-diffusion of Ga in GaAs may proceed by either the vacancy or interstitialcy mechanisms. It is possible to switch between these mechanisms with a variation of either the Fermi level or As pressure. Self-diffusion appears to be associated with Ga vacancies with charge of -3 in n-type GaAs, and Ga interstitials with charge of +2 in p-type GaAs. For intrinsic GaAs, the commonly observed V-shape in the Ga diffusivity vs As pressure plot is found to be consistent with these two diffusion mechanisms. Simple calculations can be used to predict the near-equilibrium Ga diffusivity from a single intrinsic Ga diffusion coefficient, when defined at appropriate standard conditions. A new model is presented to link the roll-over in Ga diffusivity and electron concentration at high donor concentrations.