Convergence of the formation energies of intrinsic point defects in wurtzite ZnO: first-principles study by projector augmented wave method

Electronic structure, formation energies, transition levels, and concentration of intrinsic defects in wurtzite ZnO are investigated by the projector augmented wave method in the generalized gradient approximation. Interstitials, vacancies, and antisites at different charge states are considered. Convergence of the formation energies of various intrinsic point defects is carefully checked, and comparison with earlier results is made and discussed. Even though there exists a difference for the calculated formation energies of certain defects, our calculations also show that oxygen and zinc vacancies are the dominant intrinsic donor and acceptor defects in ZnO, indicating a consistency among results by different methods. The oxygen vacancy is not expected to be the main source of strong n-type conductivity in the unintentionally doped ZnO, due to its deep level in the bandgap, but it must be the origin of the experimentally observed visible photoluminescence band centred between 2.3 and 2.5 eV.