Theoretical Study of Oxygen-Vacancy Distribution in In₂O₃

In2O3 is of particular interest as a wide-gap transparent semiconductor oxide, in which the shallow donor defect of the oxygen vacancy plays an important role in electronic properties. Herein, we focus on the oxygen vacancy with various concentrations in In2O3, where the distribution is found to be crucial to the structural stabilities. For a specific supercell, the formation energies of oxygen-vacancy pairs remarkably depend on the distance between the two vacancies, which can be used to determine the oxygen-vacancy distribution in the nonstoichiometric In2O3 structure. Interestingly, when two oxygen vacancies share a same In atom, the structures are approximately stabilized with the decreasing of distance. However, when two oxygen vacancies are not attached to the same In atom, the structures become more stable with the increasing of distance between vacancies. In addition, the gap states induced by oxygen vacancies move toward the valence band maximum (VBM) when the nearest distance between the two vacancies decreases, which will have a great effect on the conductivity.