Electronic structure of defects and doping in ZnO: Oxygen vacancy and nitrogen doping

Our recent calculations of the oxygen vacancy in ZnO based on the local density approximation with Hubbard U corrections (LDA + U) are compared with experimental deep level transient spectroscopy (DLTS) results and found to give excellent agreement for the 2+/0 and 2+/+ transition levels. While N O gives a deep acceptor level in ZnO, we show that N2 on the Zn‐site can give a shallow acceptor. Results of hybrid functional and generalized gradient approximation are compared. Calculations for the g‐factor and analysis of the wave function character also show that an electron paramagnetic resonance (EPR) center for N2 in ZnO also corresponds to the Zn‐site rather than O‐site.The observation of a donor–acceptor pair recombination photoluminescence center at 3.235 eV along with the EPR center suggests that the latter and its associated shallow acceptor level at 165 meV correspond both to the N2 on Zn. Finally, we discuss how N2 may be preferentially incorporated on the Zn site on Zn‐polar surfaces and under Zn‐poor, O‐rich conditions. While atomic nitrogen on the oxygen site in ZnO has too deep a level for p‐type doping, a nitrogen molecule sitting on the Zn site is shown by means of first‐principles calculations to have a shallow delocalized defect state suitable for p‐type doping. The hyperfine structure and g‐factor of the proposed N2 on Zn model are consistent with a previously observed Electron Paramagnetic Resonance center in ZnO.