P-type single-crystalline ZnO films obtained by (Li, N) dual implantation through dynamic annealing process
Single-crystalline ZnO films were grown on c-plane sapphire substrates by plasma-assisted molecular beam epitaxy technique. The films have been implanted with fixed fluence of 30 keV Li and 80 keV N ions at 460 °C. It is shown that dually-implanted single crystalline ZnO films exhibit p-type characteristics with hole concentration in the range of 2.5 × 1015–2.3 × 1016 cm−3, hole mobilities between 0.8 and 1.04 cm2 V−1 s−1, and resistivities in the range of 328.9–2081 Ω cm by Hall-effect measurements. The ZnO film exhibit (0002) (c-plane) orientation with no secondary phase appearing after implantation as identified by the X-ray diffraction pattern. It is confirmed that Li and N ions were effectively implanted and successfully behave as acceptor measured by XPS and SIMS results. Also compared to other similar studies, lower amount of Li and N ions make p-type characteristics excellent. It is concluded that Li and N ion implantation and dynamic annealing play a critical role in forming p-type single-crystalline ZnO films.