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

Abstract

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 $0.29\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ 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 $25\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$. 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).