Self-vacancies in Gallium Arsenide: an ab initio calculation

TL;DR

This study uses first-principles density-functional calculations to analyze vacancies in GaAs, revealing stable charge states and transitions, and confirming experimental findings with detailed geometric and energetic descriptions.

Contribution

It provides a comprehensive ab initio analysis of vacancy properties in GaAs, including charge states, stability, and relaxation geometries, expanding understanding beyond previous experimental and theoretical work.

Findings

Gallium vacancies are stable in multiple charge states, with V_Ga^-3 being dominant.

Arsenic vacancies exhibit negative-U transitions, stabilizing only specific charge states.

Resonant bond relaxation occurs for V_As^-3, similar to silicon and GaAs divacancies.

Abstract

We report here a reexamination of the static properties of vacancies in GaAs by means of first-principles density-functional calculations using localized basis sets. Our calculated formation energies yields results that are in good agreement with recent experimental and {\it ab-initio} calculation and provide a complete description of the relaxation geometry and energetic for various charge state of vacancies from both sublattices. Gallium vacancies are stable in the 0, -, -2, -3 charge state, but V_Ga^-3 remains the dominant charge state for intrinsic and n-type GaAs, confirming results from positron annihilation. Interestingly, Arsenic vacancies show two successive negative-U transitions making only +1, -1 and -3 charge states stable, while the intermediate defects are metastable. The second transition (-/-3) brings a resonant bond relaxation for V_As^-3 similar to the one identified for silicon and GaAs divacancies.