Positron annihilation spectroscopy was used to study the depth distributions and species of defects in N-, Ge-, and N/Ge-implanted material at doses of 1015/cm2. In all of the implanted samples, the Ga vacancies introduced by ion implantation were found to diffuse into much deeper regions of the GaN layers during implantation, and change into some other vacancy-type defect during annealing at 1300C. In particular, markedly different defects were found to be newly created in the electrically activated regions of both Ge- and N/Ge-implanted samples after annealing; thus indicating that these new defects were probably associated with the presence of implanted Ge dopant atoms.

Defects in N/Ge Co-Implanted GaN Studied by Positron Annihilation. Y.Nakano, T.Kachi: Journal of Applied Physics, 2002, 91[2], 884-6