Electronic structure of neutral and charged vacancies in GaAs

We have performed self-consistent tight-binding calculations on the neutral and charged states of the undistorted Ga and As vacancies in GaAs with the Lanczos-Haydock recursion method. For neutral states, defect potentials on the first- and second-nearest neighbors of a vacancy are obtained by a charge-neutrality condition, while for charged states these potentials are determined self-consistently. A discussion of the nature of both anion and cation vacancies in III-V compound semiconductors in terms of the bulk properties is given. The general characteristics of the electronic structure of the vacancies in GaAs are extracted from a detailed calculation and analysis in the case where a vacancy is neutral. In addition, we have calculated the electronic structure for the various charge states of the vacancies in GaAs. The predicted trends for the bound electron states in the gap are presented. Our results agree well with the self-consistent local-density-theory calculation for GaAs:${\mathit{V}}_{\mathrm{Ga}}^0$ and GaAs:${\mathit{V}}_{\mathrm{As}}^0$ of Bachelet et al. and with the recently published positron-annihilation-spectroscopy data for two charge-state transitions of the arsenic vacancy, ${\mathit{V}}_{\mathrm{As}}^{2\mathrm{-}}$→${\mathit{V}}_{\mathrm{As}}^{\mathrm{-}}$ and ${\mathrm{V}}_{\mathrm{As}}^{\mathrm{-}}$→${\mathit{V}}_{\mathrm{As}}^0$, by Corbel et al.