First-principles calculations were presented for stable and metastable geometries of various H-related configurations in p-type GaN, including isolated interstitial H as well as Mg-H and Be-H complexes. The associated vibrational stretching and wagging modes were also calculated; systematically including anharmonic contributions to the vibrational frequencies. The anharmonicity was large, due to the light mass of the H atom. Based upon investigations of a large number of configurations, a correlation was derived between the vibrational frequency of the stretching mode and the bond length in the N-H bond. The results were compared with experimental results. In particular, a new configuration for the Mg-H complex was proposed that agreed with the geometrical information extracted from polarization-dependent infra-red spectroscopy.

Identification of Hydrogen Configurations in p-Type GaN through First-Principles Calculations of Vibrational Frequencies. S.Limpijumnong, J.E.Northrup, C.G. Van de Walle: Physical Review B, 2003, 68[7], 075206 (14pp)