Stability and electronic properties of native defects and substitutional impurities in GaN nanotubes

Abstract

Spin-polarized density functional theory is used to investigate the stability and electronic properties of vacancies, antisites, and substitutional Si and C in zigzag and armchair GaN nanotubes. Antisites and vacancies present lower formation energies as compared with their counterparts in the bulk GaN system, introducing localized electronic levels within the nanotube band gap. For vacancy systems in the neutral charge state the defective levels present a spin splitting giving rise to a net magnetic moment of 1 μB. Substitutional Si and C in the Ga site have the lowest formation energy and exhibit donor properties, suggesting the formation of defect-induced n-type GaN nanotubes. Our calculated formation energies for charged defects indicate that the neutral charge states are present for all the studied defects, thus suggesting a different picture for those defects in nanotube systems when compared with their counterparts in the bulk phase.