Effect of N/Ge co-implantation on the Ge activation in GaN

N-type regions have been produced in undoped GaN films by Ge and N/Ge implantation, sequentially, and subsequent annealing with a ${\mathrm{SiO}}_{\mathrm{2}}$ encapsulation layer at 1300 °C. Improved Ge-doping characteristics have been achieved for GaN by N/Ge co-implantation, attaining activation efficiencies above 95%, whereas in the case of conventional Ge implantation, the activation efficiency is low owing to the generation of N vacancies. In particular, overlapping of the N-implanted region with the Ge one can make the Ge activation higher at a N/Ge ratio of ∼1. Therefore, the co-implantation of additional N atoms drastically enhances the Ge activation based on a site-competition effect.