Gallium self-interstitial relaxation in Gallium Arsenide: an {ab initio} characterization

TL;DR

This study uses ab initio simulations to characterize gallium interstitials in GaAs, identifying stable configurations and charge states, and aligns well with experimental findings.

Contribution

It provides a detailed ab initio analysis of gallium interstitial configurations and charge states in GaAs, highlighting the importance of finite size effects.

Findings

Gallium interstitials prefer tetrahedral sites surrounded by Ga atoms.

Predominant charge states depend on doping conditions (+1, neutral, -1).

Results agree with recent experimental data.

Abstract

Ga interstitials in GaAs ($I_{Ga}$) are studied using the local-orbital {ab-initio} code SIESTA in a supercell of {216+1} atoms. Starting from eight different initial configurations, we find five metastable structures: the two tetrahedral sites in addition to the 110-split$\mathrm{_{[Ga-As]}}$, 111-split$\mathrm{_{[Ga-As]}}$, and 100-split$\mathrm{_{[Ga-Ga]}}$. Studying the competition between various configuration and charges of $I_{Ga}$, we find that predominant gallium interstitials in GaAs are charged +1, neutral or at most -1 depending on doping conditions and prefer to occupy the tetrahedral configuration where it is surrounded by Ga atoms. Our results are in excellent agreement with recent experimental results concerning the dominant charge of $I_{Ga}$, underlining the importance of finite size effects in the calculation of defects.