A first-principles study of oxygen vacancies in MgxZn1−xO alloys was presented. Different types of oxygen vacancies were distinguished by their number of Mg and Zn nearest neighbours. The formation energy was found to be lowest for vacancies surrounded by four Zn nearest neighbours and was almost independent of the overall concentration in the alloy. Since this energy of formation enters the concentration via a Boltzmann factor, it implied that vacancies other than purely Zn surrounded were very unlikely even in relatively Mg-rich alloys. The defect energy level associated with the vacancy was a very deep donor level closer to the valence band than the conduction band. It did not follow the band gap with concentration but stays approximately fixed relative to the valence-band maximum. The defect level gradually increases with number of Mg neighbours.

First-Principles Study of Oxygen Vacancies in MgxZn1−xO Alloys. A.Boonchun, W.R.L.Lambrecht: Physical Review B, 2010, 81[2], 024103