Self-consistent calculations of the electronic structure for ideal Ga and As vacancies in GaAs

Abstract

Self-consistent calculations for both types of vacancies in a polar semiconductor are presented. The study is carried out by the Green's-function method proposed by Baraff and Schl\"uter and applied to the silicon vacancy. The GaAs band structure was obtained by a self-consistent pseudopotential calculation based on localized orbitals only. The Green's function for the perfect crystal was then expanded in the same basis set, and both vacancies were separately studied. Owing to the polar nature of the host semiconductor, the self-consistent treatment was necessary to obtain reliable results. The Ga vacancy has a very weakly bound state almost degenerate with the top of the valence band, while the As vacancy has a deep bound-state level, 1.08 eV above the top of the valence band. The As vacancy also gives rise to an overall modification of the density of states very similar to the case of the ideal silicon vacancy. Modifications of these results due to lattice-relaxation effects are discussed in light of available experimental data.