First-principles calculations based on hybrid Hartree-Fock density functionals provide a clear picture of the defect energetics and electronic structure in ZnO. Among the donor-like defects, the O vacancy and H impurity, which were deep and shallow donors, respectively, were likely to form with a substantial concentration in n-type ZnO. The Zn interstitial and Zn antisite, which were both shallow donors, were energetically much less favorable. A strong preference for the O vacancy and H impurity over the acceptor-like Zn vacancy was found under O-poor conditions, suggesting that the O vacancy contributed to non-stoichiometry and that H acts as a donor, both of which were without significant compensation by the Zn vacancy. The present results were consistent with the relevant experimental observations.

Defect Energetics in ZnO - a Hybrid Hartree-Fock Density Functional Study. Oba, F., Togo, A., Tanaka, I., Paier, J., Kresse, G.: Physical Review B, 2008, 77[24], 245202