Positron annihilation spectroscopy was used to determine the nature and concentration of open-volume defects in as-grown and electron irradiated (2MeV, 6 x 1017/cm2) samples. The Zn vacancies were found to have concentrations of about 2 x 1015/cm3 in the as-grown material and about 2 x 1016/cm3 in the irradiated material. The concentrations were in very good agreement with the total acceptor density, as determined by temperature-dependent Hall experiments. The Zn vacancies were therefore the predominant acceptors in both as-grown and irradiated ZnO.

Evidence of the Zn Vacancy Acting as the Dominant Acceptor in n-Type ZnO. Tuomisto, F., Ranki, V., Saarinen, K., Look, D.C.: Physical Review Letters, 2003, 91[20], 205502