Vacancy profiles and clustering in light-ion-implanted GaN and ZnO

We present experimental results obtained in H-implanted GaN and He- and Li-implanted ZnO. The ion energies were varied in the range 100-850 keV, and the implantation fluences in the range 5 × 1013 to 1 × 1018 cm−2. In addition, conventional and flash anneals at temperatures 500-1400 °C were performed on the ZnO samples. The data obtained with a slow positron beam show that vacancy clusters are formed in as-implanted samples with fluences above 1 × 1017 cm−2. Below this value only single vacancies are detected after implantation, but vacancy clusters can be formed and subsequently dissociated by thermal annealings.