Atomic configurations corresponding to local-energy minima for the neutral MgH complex in wurtzite GaN were identified by using density-functional theory and the generalized-gradient approximation for exchange and correlation. MgH binding energies, H local-mode vibration frequencies, and configurational degeneracies for the six lowest-energy configurations were used, along with corresponding results for isolated H+, to compute equilibrium H state populations in Mg-doped GaN as a function of temperature. For a Mg concentration of 1019/cm3 and a H/Mg concentration ratio of 0.99, MgH was found to be the majority H species at room temperature with isolated H+ becoming the majority species at about 550C. Among the MgH states, one was found to predominate at all temperatures. The dominant configuration consists of H at an antibonding site of a N neighbor of the substitutional Mg, with the Mg–N and N–H bonds nearly aligned and the N–H bond oriented at an angle of ~109° with respect to the c-axis. The H stretch-mode frequency of the dominant state was consistent with the peak observed in Fourier-transform infrared reflection spectra from Mg-doped GaN samples.

Configurations, Energies and Thermodynamics of the Neutral MgH Complex in GaN. A.F.Wright, S.M.Myers: Journal of Applied Physics, 2003, 94[8], 4918-22