Ion-implantation induced defects in ZnO studied by a slow positron beam

Introduction and annealing behavior of defects in Al+-implanted ZnO have been studied using an energy variable slow positron beam. Vacancy clusters are produced after Al+-implantation. With increasing ion dose above 1014 Al+/cm2 the implanted layer is amorphized. Heat treatment up to 600 C enhances the creation of large voids that allow the positronium formation. The large voids disappear accompanying the recrystallization process by further heat treatment above 600 C. Afterwards, implanted Al impurities are completely activated to contribute to the n-type conduction. The ZnO crystal quality is also improved after recrystallization. (orig.)