Hydrogen configurations, formation energies, and migration barriers were obtained from density-functional theory calculations employing the generalized-gradient approximation for exchange and correlation. The H configurations and formation energies were similar to previous density-functional theory results obtained by using the local-density approximation for exchange and correlation with the most notable differences being higher formation energies for H0 (0.2eV) and H2 (0.1eV) in the generalized-gradient approximation calculations and a preference for H+ at a bond-centered site. Generalized-gradient approximation H migration barriers differ from local-density approximation values with the largest differences being 0.4eV higher generalized-gradient approximation H+ migration barriers. Refined measurements of field-induced H+ drift in GaN p/n+ diodes had also been performed. Modeling of these results indicated that the sum of the H+ diffusion activation energy and the H+ binding energy to ionized Mg acceptors was 1.76eV. The corresponding generalized-gradient approximation result of 1.6eV was in good agreement with the measured value.

Hydrogen Configurations, Formation Energies and Migration Barriers in GaN. A.F.Wright, C.H.Seager, S.M.Myers, D.D.Koleske, A.A.Allerman: Journal of Applied Physics, 2003, 94[4], 2311-8