Vacancy Defects as Compensating Centers in Mg-Doped GaN

We apply positron annihilation spectroscopy to identify [Formula presented] complexes as native defects in Mg-doped GaN. These defects dissociate in postgrowth annealings at [Formula presented]. We conclude that [Formula presented] complexes contribute to the electrical compensation of Mg as well as the activation of [Formula presented]-type conductivity in the annealing. The observation of [Formula presented] complexes confirms that vacancy defects in either the N or Ga sublattice are abundant in GaN at any position of the Fermi level during growth, as predicted previously by theoretical calculations.