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 ${\mathit{V}}_{\mathrm{As}}^{3+}$ is competitive with that of the gallium interstitial ${\mathrm{Ga}}_{\mathit{i}}^{3+}$. After a breathing-mode relaxation, which reduces the energy by more than 1.5 eV, the nearest-neighbor Ga atoms exhibit a nearly ${\mathrm{sp}}^2$ bonding configuration. On the basis of our results we propose that charged anion vacancies with ${\mathrm{sp}}^2$-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 self-diffusion in these materials.