Effects of nitrogen vacancies on transition-metal-doped GaN: An ab initio study

The effects of N vacancies on the transition metal (Cr, Mn, Fe, Co, Ni, and Cu) doped GaN have been studied at the levels of the local spin density approximation (LSDA) and LSDA+U (Coulomb interaction). Our calculations show that the N vacancy favorably exists near a transition metal ion and the interaction between transition metal ion and N vacancy is insensitive to the distance when exceeding 3.3 A. Furthermore, we find that the existed N vacancies alter the magnetic moments of the doped GaN, where the magnetic moments increase for Cr or Mn doped GaN, and decrease for Fe, Co, Ni, or Cu doped GaN. This result can be interpreted well by the Hund's multiplicity rules. However, it is found that the magnetic moments of doped GaN with N vacancies are insensitive to the distances between N vacancies and the doped transition metal ions. Our obtained results are useful to elucidate the effects of N vacancies on the magnetic properties of the transition metal doped GaN.