Vacancies and interstitials in indium nitride: Vacancy clustering and molecular bondlike formation from first principles

Abstract

We investigate the structural and electronic properties and formation energies of vacancy, interstitial, and antisite defects, as well as complex formation, in wurtzite InN using first-principles calculations. The N interstitial, which forms a split-interstitial configuration with a ${\text{N}}_2$-like bonding, has the lowest formation energy under N-rich conditions in $p$-type material, where it is a triple donor. We find that indium vacancies have a tendency to form “clusters,” which results in local nitrogen-rich regions and the formation of ${\text{N}}_x$-molecular-like bonds. These complexes are amphoteric, have a relatively high formation energy, and are formed more readily under N-rich conditions. The nitrogen vacancy is a low energy defect under more In-rich conditions, and in $p$-type material it acts as a single and triple donor. In the neutral and negative charge states, we find nitrogen vacancies also prefer to be situated close to one another and to cluster, giving rise to local In-rich regions with electron localization at these metalliclike bonding configurations. The indium antisite in the $4+$ charge state is the lowest-energy defect under In-rich conditions in $p$-type material and thus also acts as a donor. Our findings shed light on, and help explain, recent and sometimes conflicting, experimental observations.