The behavior of H was investigated in unintentionally doped GaN epilayers, on sapphire substrates, which had been grown by means of NH3 molecular beam epitaxy. It was found, using nuclear reaction analysis, that the background electron concentration increased with increasing H concentration. This suggested that there existed a H-related donor in undoped GaN. Fourier-transform infra-red absorption and X-ray photo-electron spectroscopy also revealed that the H atom was bound to N atoms; with a local vibrational mode at about 3211/cm. It was therefore proposed that the H-related complex, Ga…H-N, was a H-related donor candidate and was partly responsible for the high n-type background which was commonly observed. Raman spectroscopy showed that, in addition to the expected compressive biaxial strain, some films suffered appreciable tensile biaxial strain. This anomalous behavior was explained in terms of interstitial H lattice dilation.

Hydrogen Behavior in GaN Epilayers Grown by NH3-MBE. M.Y.Kong, J.P.Zhang, X.L.Wang, D.Z.Sun: Journal of Crystal Growth, 2001, 227-228, 371-5