Effects of vacancy defects on the electronic structure and optical properties of GaN:Fe

Abstract

Using first-principles calculations based on the density functional theory, we investigated the photoelectric properties of GaN and 6.25% Fe doped GaN both containing nitrogen vacancy (VN) and gallium vacancy (VGa) defects. By analyzing the band structure, electronic state distribution, dielectric function, absorption coefficient, refractive index, reflectivity, energy loss spectrum and extinction coefficient, the influences of vacancy defects on the electronic structure and optical properties of the doping system were systematically discussed. Our results predict that N defect GaN:Fe is indirect band gap semiconductor whereas Ga defect GaN:Fe is direct band gap semiconductor. The VN is a kind of donor defect, which leads to the rise of the Fermi level; while the VGa is an acceptor defect which introduces spin polarized defect states near the forbidden band. The native vacancy point defects in the host will cause significant changes to the optical properties near the low energy region. On the other hand, the introduction of Fe will suppress this phenomenon, indicating that the incorporation of Fe will improve the insulation of the material and thus endow the material with semi-insulation.