Mg-O and Mg-VN defect complexes in cubic GaN

Mg-O and Mg-V-N defect complexes in cubic GaN are examined by means of ab initio calculations using a supercell approach in connection with the full-potential linear muffin-tin-orbital method. 32-atom supercells are used, and atomic relaxations are taken into account. The positions of the defect levels and formation energies are calculated and discussed in comparison with the results for individual defects. The calculations show, in agreement with experimental data, that both complexes, Mg-O and Mg-V-N, are energetically favorable in GaN, and should play an important role in the self-compensation mechanism. Both kinds of complexes introduce resonant states in the valence and conduction bands.