Migration of Ga vacancies and interstitials in ?-Ga2O3

Pathways and energy barriers for the migration of Ga vacancies (VGa) and Ga interstitials (Gai) in-Ga2O3 are explored using hybrid functional calculations and the nudged elastic band method. Considering-Ga2O3 as primarily being an n-type semiconductor, we focus on defect charge states relevant under such conditions: V 3- Ga, Gai3+, and Gai+. Notably, we describe a mechanism by which VGa can transform between its different split configurations. In all cases, the intermediate state consists of a vacancy split between three Ga sites-a three-split vacancy-which enables passage over a significantly lower energy barrier. This is because it avoids the unfavorable simple vacancy at the tetrahedral Ga site. The proposed mechanism lowers the overall barrier for V 3- Ga diffusion along the [001] crystal direction from 1.73 to 0.97 eV, whereas the 2.08 eV barrier for the [100] and [010] directions is unaffected. For Gai3+, we obtain similar overall migration barriers of 0.72, 0.80, and 1.02 eV for the [010], [001], and [100] directions, respectively. Gai+ exhibits a strong preference for diffusion within the large eight-sided channel; the overall migration barrier is 0.92 eV for the [010] direction, and 2.16 eV for the [001] and [100] directions. The limiting step for the two latter directions involves ionization of Gai+ followed by a jump to an adjacent large eight-sided channel as Gai3+. Our results are discussed in light of experimental observations of thermally activated recovery processes in irradiated material.