Structure and Migration Mechanisms of Oxygen Interstitial Defects in β-Ga2O3

Abstract

Geometric configurations of oxygen interstitial (Oi) defects in β-Ga2O3 are studied using an intensive search strategy and optimized with density functional theory using PBEsol and PBE0-TC-LRC functionals. The results show that Oi atoms can form O–O dimers at three different O sites in β-Ga2O3 as oxygen split-interstitial defects in 0 and +1 charge states. At higher Fermi levels above 1 eV from the conduction band minimum, trapping of extra electrons can break the O–O dimer, forming bulk (Formula presented.) and (Formula presented.) configurations. The investigation of O–O dimer migration mechanisms in β-Ga2O3 reveals that dimers move between rings through bond-breaking and rotation processes with activation barriers of ≈1 and 0.3 eV, respectively. (Formula presented.) can migrate to neighboring rings with a much lower barrier of 0.15 eV. These results provide a detailed map of the potential energy surface of Oi in β-Ga2O3 and demonstrate how interstitial O can migrate between different rings.