Positron annihilation spectroscopy was used to identify VN–MgGa complexes as being native defects in Mg-doped GaN. These defects dissociate in post-growth annealing at 500–800C. It was concluded that VN–MgGa complexes contributed to the electrical compensation of Mg as well as the activation of p-type conductivity in the annealing. The observation of VN–MgGa complexes confirmed that vacancy defects in either the N or Ga sub-lattice were abundant in GaN at any position of the Fermi level during growth, as predicted previously by theoretical calculations.

Vacancy Defects as Compensating Centers in Mg-Doped GaN. S.Hautakangas, J.Oila, M.Alatalo, K.Saarinen, L.Liszkay, D.Seghier, H.P.Gislason: Physical Review Letters, 2003, 90[13], 137402 (4pp)