In the framework of density functional theory, using the plane-wave pseudopotential method, the N vacancy (VN) in both wurtzite and zincblende AlN was studied by the super-cell approach. The atom configuration, density of states, and formation energies of various charge states were calculated. Two defect states were introduced by the defect, which were a doubly occupied single state above the valance band maximum and a singly occupied triple state below the conduction band minimum for wurtzite AlN and above the conduction band minimum for zincblende AlN. So VN acts as a deep donor in wurtzite AlN and a shallow donor in zincblende AlN. A thermodynamic transition level E(3+/+) with very low formation energy appears at 0.7 and 0.6eV above the valance band maximum in wurtzite and zincblende structure respectively, which may have a wide shift to the low energy side if atoms surrounding the defect were not fully relaxed. Several other transition levels appear in the upper part of the band-gap. The number of these levels decreased with the structure relaxation. However, these levels were unimportant to AlN properties because of their high formation energy.

First Principle Study of Nitrogen Vacancy in Aluminium Nitride. H.G.Ye, G.D.Chen, Y.Z.Zhu, H.M.Lü: Chinese Physics, 2007, 16[12], 3803-8