Density functional theory was used to investigate the formation, properties, and atomic configurations of vacancies, antisite defects and interstitials in GaN, and the density functional theory results were compared with those calculated by molecular dynamics simulations using 2 representative potentials. The density functional theory calculations revealed that the relaxation of vacancies was generally small, but the relaxation around antisite defects was large, especially for the Ga antisite that was not stable and converted to a N+-N <00▪1> split interstitial plus a Ga vacancy at the original site. The N interstitials, starting from all possible sites, eventually relaxed into a N+-N <11▪0> split interstitial. In the case of Ga interstitials, the most stable configuration was a Ga octahedral interstitial, but the energy difference among all the interstitials was small. The Ga+-Ga <11▪0> split interstitial could bridge the gap between non-bonded Ga atoms, thereby leading to a chain of four Ga atoms along the <11▪0> direction in GaN. The formation energies of vacancies and antisite defects obtained by using the Stillinger-Weber potential were in reasonable agreement with those obtained by density functional theory calculations, whereas the Tersoff-Brenner potential better described the behavior of N interstitials. In the case of Ga interstitials, the most stable configuration predicted by the Tersoff-Brenner model was a Ga+-N <11▪0> split interstitial; while for the Stillinger-Weber model the Ga tetrahedral configuration was more stable, which was in contrast to density functional theory results.

Intrinsic Defect Properties in GaN Calculated by ab initio and Empirical Potential Methods. F.Gao, E.J.Bylaska, W.J.Weber: Physical Review B, 2004, 70[24], 245208 (8pp)