First-principles Investigation on Diffusion Mechanism of Zinc in n-GaSb

Abstract

According to previous investigations, Zn diffusion in GaSb is mediated by dissociative mechanism or kick out mechanism. However, little work has been carried out to explain why Zn diffusion is mediated by these two different diffusion mechanisms. This work concentrated on the effect of diffusion sources (pure Zn and ZnGa alloy) on the diffusion mechanism mediating Zn diffusion in n-GaSb. First-principles method was employed to calculate the formation energies and migration barriers for interstitial Zn in all possible charges states at two tetrahedral sites. It was found that diffusion sources can influence the site of interstitial Zn, resulting in different diffusion mechanisms. Interstitial Zn is stable at anion-surrounded tetrahedral site under pure Zn condition, while stable at cation-surrounded tetrahedral site under ZnGa alloy condition. The results of diffusion activation energies demonstrated that kick out mechanism plays a dominant role for Zn diffusion in n-GaSb under ZnGa condition, and that under pure Zn condition, dissociative mechanism plays a dominant role at the beginning of the diffusion process and then kick out mechanism becomes dominant.