Evidence of strong acceptor peaks in ZnO thin films doped with phosphorus by plasma immersion ion implantation technique

The photoluminescence of ZnO films implanted with phosphorus ions using plasma immersion ion implantation has been studied. The samples were rapid thermal annealed at 700–1000 °C. A dominant acceptor-bound exciton (A°X) peak around 3.35 eV was observed for the sample annealed at 1000 °C with no evidence of donor bound exciton peak at 3.36 eV. Moreover, the free electron-to-acceptor peak at 3.31 eV and the donor-to-acceptor pair peak at 3.22 eV certify the presence of acceptors in the annealed samples. I–V performed on p-ZnO/n-Si heterojunction diode clearly exhibited a rectifying behavior with a threshold voltage of 3.3 V. The results have been stable even after 5 months. These results show a promising method for achieving stable p-type ZnO films.