Role of point defects in the electrical and optical properties of In2O3

Abstract

Using hybrid density-functional calculations we investigate the effects of native point defects on the electrical and optical properties of ${\mathrm{In}}_{2}{\mathrm{O}}_{3}$. We analyze formation energies, transition levels, and local lattice relaxations for all native point defects. We find that donor defects are in general more energetically favorable than acceptor defects, except near O-rich conditions, where oxygen interstitials and indium vacancies have low formation energy in $n$-type ${\mathrm{In}}_{2}{\mathrm{O}}_{3}$. The oxygen vacancy is the lowest-energy donor defect with transition level $(2+/+)$ slightly below and $(+/0)$ slightly above the conduction-band minimum (CBM), with a predicted luminescence peak at 2.3 eV associated with the transition ${V}_{\mathrm{O}}^{0}\phantom{\rule{4pt}{0ex}}\ensuremath{\rightarrow}\phantom{\rule{4pt}{0ex}}{V}_{\mathrm{O}}^{+}$. Despite being a shallow donor, the oxygen vacancy becomes electrically inactive for Fermi levels at or higher than $\ensuremath{\sim}0.1$ eV above the CBM. This indicates that conductivity due to oxygen vacancies will saturate at rather low carrier concentrations when compared to typical carrier concentrations required for transparent conducting oxides in many device applications.