Regions of n-type material were produced in undoped GaN films by Ge and N/Ge sequential implantation and subsequent annealing (under a SiO2 encapsulation layer) at 1300C. Improved Ge-doping characteristics were achieved by N/Ge co-implantation; and attained activation efficiencies above 95%. In the case of conventional Ge implantation, the activation efficiency was low due to the generation of N vacancies. In particular, overlapping of the N-implanted region with the Ge one could make the Ge activation higher at a N/Ge ratio of about 1. It was concluded that the co-implantation of additional

N atoms markedly enhanced Ge activation which was based upon a site-competition effect.

Effect of N/Ge Co-Implantation on Ge Activation in GaN. Y.Nakano, T.Kachi: Applied Physics Letters, 2001, 79[10], 1468-70