Mg-O and Mg-V-N defect complexes in cubic GaN

Mg-O and Mg-V-N defect complexes in cubic GaN are examined by means of ab i nitio calculations using a supercell approach in connection with the full-p otential linear muffin-tin-orbital method. 32-atom supercells are used, and atomic relaxations are taken into account. The positions of the defect lev els and formation energies are calculated and discussed in comparison with the results for individual defects. The calculations show, in agreement wit h experimental data, that both complexes, Mg-O and Mg-V-N, are energeticall y favorable in GaN, and should play an important role in the self-compensat ion mechanism. Both kinds of complexes introduce resonant states in the val ence and conduction bands.