By means of hybrid functional calculations an investigation was made of  the role of native point defects in the electronic properties of InN. It was found that nitrogen vacancies were the most energetically favourable defects and acted as shallow donors for Fermi-level positions within the band gap. However, their formation energies were too high in order to explain the observed unintentional n-type conductivity in as-grown or annealed InN films. A transition from donor to acceptor behaviour occurred at 1.9eV above the valence-band maximum, indicating that if nitrogen vacancies were intentionally introduced to increase the carrier concentration, e.g., by irradiating the InN crystals, the Fermi level will saturate at 1.3eV above the conduction-band minimum. The other donor defects, i.e., the nitrogen split interstitial, nitrogen antisite, and indium antisite, had even higher formation energies, and thus were also unlikely sources of unintentional n-type conductivity. The indium vacancies and nitrogen interstitials occupying the octahedral sites were deep acceptors with transition levels resonant in the conduction band. These defects exhibited very high formation energies even for Fermi levels well above the conduction-band minimum. The results indicated that InN could support very high electron concentrations before compensation by native acceptor defects took place.

Hybrid Functional Calculations of Native Point Defects in InN. A.Janotti, J.L.Lyons, C.G.Van de Walle: Physica Status Solidi A, 2012, 209[1], 65-70