The effect of N+ and O+ implantation upon the microstructure was studied by performing K-edge X-ray absorption fine structure measurements of N. It was found that, in as-grown samples, the central N atom was 4-fold coordinated with 3.35 Ga atoms at the expected distance of 0.193nm; and 0.65 which were displaced to a distance which was greater by about 0.033nm. Implantation with N or O ions enhanced the distortion of the microstructure, and the number of displaced Ga atoms increased from 0.65 to 1. The increase of the distortion in the coordination number was attributed to the generation of excess N vacancies. Implantation also caused a reduction, in the nearest-neighbour distances, of about 2% and an increase in the Debye-Waller factor.

On the Effect of Ion Implantation on the Microstructure of GaN. M.Katsikini, J.Bollmann, W.T.Masselink, E.C.Paloura: Journal of Synchrotron Radiation, 1999, 6[3], 552-4