PNNL

Abstract

Intrinsic interstitial and antisite defects in GaN have been studied using density functional theory (DFT), and their configurations, electronic structures and bonding properties have been characterized using the Wannier function. All N interstitial configurations eventually transform into N-N split interstitials, between which two p orbitals exist. The relaxation of a Ga antisite defect also leads to the formation of a N-N split configuration; however, its local Wannier orbitals are remarkably different from the N-N split interstitial. The different local Wannier orbitals around Ga interstitial configurations demonstrate that Ga interstitials are critical defects in GaN. The electronic orbitals of the Ga octahedral interstitial is, for example, greatly delocalized, and there are no covalent bonds formed between the interstitial and the surrounded atoms. The most striking feature is that Ga-Ga split interstitials can bridge the gap between non-bonded Ga atoms, thereby leading to a chain of four metallic-like-bonded Ga atoms in GaN, which may exhibit novel quantum properties.