Stability and electronic structure of defect complexes in Gd-doped GaN: First-principles calculations

Abstract

Based on the density functional theory, we systematically investigate the stability and magnetic moment of various defect complexes, which are formed by Gd and Ga vacancies, N vacancy, N interstitial, or O interstitial in GaN doped with Gd. The point defects and dopant Gd are found to attract each other, i.e., cooperative effect, which means that defects would make it relatively easy to incorporate Gd into GaN. However, the formation of defects, especially Ga vacancies in GaN:Gd, is not energetically stable. The more discretely Ga vacancies distribute, the larger is the local magnetic moment that they can introduce in GaN:Gd. In comparison, N vacancies do not contribute to the local magnetic moment irrespective of their concentration and symmetry. For the case of the interstitial atom, the octahedral N can induce the local magnetic moment, while the tetrahedral N or O sites would not contribute to the local magnetic moment. Only the octahedral O near the Gd is found to induce the magnetic moment.