Depth-resolved cathodoluminescence, positron annihilation and surface photovoltage spectroscopy were used to determine the energy levels of Zn vacancies and vacancy clusters in bulk ZnO crystals. Doppler broadening-measured transformation of Zn vacancies to vacancy clusters with annealing shifts defect energies significantly lower in the ZnO band gap. Zn and corresponding O vacancy-related depth distributions provided a consistent explanation of depth-dependent resistivity and carrier-concentration changes induced by ion implantation.

Vacancy Defect and Defect Cluster Energetics in Ion-Implanted ZnO. Y.Dong, F.Tuomisto, B.G.Svensson, A.Y.Kuznetsov, L.J.Brillson: Physical Review B, 2010, 81[8], 081201