Binding of the N interstitial with neutral MgH in p-type GaN investigated with density functional theory

Density-functional theory and the generalized gradient approximation were utilized to investigate the interaction of N interstitials with neutral MgH centers in p-type GaN. Formation energies and the corresponding local-energy minimum configurations of the defect complex are reported along with the energy to dissociate the complex into isolated MgH and a N interstitial. The conclusion is that N interstitials will bind with MgH centers in p-type GaN(Mg,H), with binding energies of 0.71, 0.44, and 0.29eV in the +3, +2, and +1 charge states, respectively. Hydrogen local-mode vibrational frequencies for the bound complex were estimated and compared to previous results for isolated MgH. The binding of a N interstitial to MgH perturbs the H stretch-mode frequency by 25cm-1. These results are discussed in the context of recent experiments at Sandia National Laboratories, which suggest that N interstitials, created by proton irradiation, become mobile during subsequent annealing and bind with MgH centers in p-type GaN(Mg,H). © 2005 The American Physical Society.