ENERGETICS OF THE AS VACANCY IN GAAS - THE STABILITY OF THE 3+ CHARGE-STATE

Total-energy calculations predict that the As vacancy in GaAs adopts a 3+ charge state under p-type conditions, and that the formation energy of V-As(3+) is competitive with that of the gallium intrstitial Ga-i(3+). After a breathing-mode relaxation, which reduces the energy by more than 1.5 eV, the nearest-neighbor Ga atoms exhibit a nearly sp(2) bonding configuration. On the basis of our results we propose that charged anion vacancies with sp(2)-bonded cation neighbors should be examined as possible mechanisms for the compensation of p-type doping in III-V and II-VI semiconductors, and as possible facilitators of acceptor diffusion and anion selfdiffusion in these materials.