Abstract :
This paper consists of three parts. In the first part, current understanding on intrinsic point-defect equilibria in GaAs is reviewed. Regarding defect equilibria in the bulk, the amphoteric native defect (AND) model is outlined to indicate the Ga vacancy equilibrium concentration. In the second part, the model is extended to include surface Fermi-level pinning in order to predict the profile of the equilibrium concentration of Ga vacancies in the sub-surface layers. The extension generalizes the formation kinetics of point defects and naturally derives a surface “bottle-neck effect” for point-defect formation: The surfaces do not always act as perfect sinks or sources for intrinsic point-defect formation through Schottky-type defect formation which has generally been assumed. Dislocations induce a bulk “bottle-neck effect” by which they do not always act as perfect sinks and sources. In the third part, diffusivity data of plasma-induced intrinsic point defects at low temperature are presented with high-temperature data of vacancies. They are of an acceptor-type and highly mobile even at room temperature. The point defects are suggested to be interstitials rather than vacancies.
