An investigation was made of  the role of the O-vacancy in ZnO. The vacancy was well-known to be rich in ZnO and the origin of the natural n-type conductivity. The electronic structure of the O-vacancy examined by the accurate GW calculations indicates that it was a deep donor. By considering the interactions between the O-vacancy and the other native point defects in O-deficient ZnO through density-functional theory calculations, the presence of O-vacancy induces the formation of Zn-interstitial which was a shallow donor. A quantum mechanical attractive interaction between the deep O-vacancy donor and the shallow Zn-interstitial donor, which came from the electronic orbital hybridization, was considered.

GW Calculation of O-Vacancy and Interactions between Native Point Defects in O-Deficient ZnO. Kim, M.S., Kim, Y.S., Park, C.H.: Current Applied Physics, 2011, 11[3], S288–91