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