Undoped single crystals were implanted with multiple-energy (50 to 380keV) N+ ions to doses ranging from 1012 to 1014/cm2. Positron annihilation measurements showed that vacancy defects were introduced into the implanted layers. The concentrations of the vacancy defects increased with increasing ion dose. The annealing behavior of the defects could be divided into 4 stages which correspond to the formation and recovery of large vacancy clusters and the formation and disappearance of vacancy–impurity complexes. All of the implantation-induced defects were removed by annealing at 1200C. Cathodoluminescence measurements showed that the implantation-induced defects acted as non-radiative recombination centers to suppress ultra-violet emission. After annealing, these defects disappeared gradually and the ultra-violet emission reappeared. This coincided with positron annihilation measurements.

N+ Ion-Implantation-Induced Defects in ZnO Studied with a Slow Positron Beam. Chen, Z.Q., Sekiguchi, T., Yuan, X.L., Maekawa, M., Kawasuso, A.: Journal of Physics - Condensed Matter, 2004, 16[2], S293-9