Structure and Migration Mechanisms of Oxygen Interstitial Defects in β‐Ga ₂ O ₃

Geometric configurations of oxygen interstitial (O i ) defects in β‐Ga 2 O 3 are studied using an intensive search strategy and optimized with density functional theory using PBEsol and PBE0‐TC‐LRC functionals. The results show that O i atoms can form O–O dimers at three different O sites in β‐Ga 2 O 3 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 and configurations. The investigation of O–O dimer migration mechanisms in β‐Ga 2 O 3 reveals that dimers move between rings through bond‐breaking and rotation processes with activation barriers of ≈1 and 0.3 eV, respectively. 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 O i in β‐Ga 2 O 3 and demonstrate how interstitial O can migrate between different rings.