Two absorption bands, located at about 1730 and 2960/cm in the infra-red absorption spectra, were observed in undoped samples which had been grown using low-pressure metal-organic vapor phase epitaxy, irradiated with γ-rays, and exposed to a radio-frequency H plasma. Proton implantation, followed by γ-irradiation, could also activate the infra-red band at around 1730/cm. On the basis of the experimental results, the 1730/cm band was tentatively attributed to the local vibrational modes of Ga-H complexes in the vicinity of N vacancies. The 2960/cm band was attributed to the local vibrational modes of N-H complexes in the vicinity of Ga vacancies, or of C-H complexes.

J.Q.Duan, B.R.Zhang, Y.X.Zhang, L.P.Wang, G.G.Qin, G.Y.Zhang, Y.Z.Tong, S.X.Jin, Z.J.Yang, X.Zhang, Z.H.Xu: Journal of Applied Physics, 1997, 82[11], 5745-7