Ab initio calculations of structural and energetic properties of defects in gallium nitride

Abstract

Ab initio total energy calculations have been performed to investigate the properties of intrinsic defects in GaN. It is found that the nitrogen defects are more stable than the Ga defects under nitrogen-rich conditions, and the results are generally consistent with those obtained by recent first-principles calculations. For the four types of nitrogen interstitials investigated, relaxation of all configurations leads to a N–N⟨112¯0⟩ split configuration. The most stable configuration for Ga interstitials is the Ga octahedral interstitial, but the energy difference between the octahedral and tetrahedral configurations is small (<0.35 eV) and depends on the basis set employed. While the ⟨N–N⟩ bond distance in the N–N split interstitial is very close to that of a free N2 molecule, the Mulliken charge analysis indicates that the N atoms are partially charged, which is in contrast with previous theoretical suggestions. Based on the calculated results, the relative stabilities of various defects in GaN are determined.