Hole concentrations and Mg-related photoluminescence bands in metal-organic chemical vapor-deposited Mg-doped material were investigated as a function of the Mg concentration. The hole density was found to reach a maximum for a Mg content of about 3 x 1019/cm3. When the Mg concentration was increased beyond this value, the hole density dropped rapidly. Analysis of the photoluminescence spectra revealed that, near to the maximum hole concentration, the predominant radiative recombination mechanism changed from a free-to-bound to a donor-acceptor pair transition. The results strongly indicated that self-compensation effects limited the hole density. On the basis of theoretical predictions, and data on acceptor-doped II-VI compounds, it was proposed that the deep-donor which was involved in self-compensation was a nearest-neighbor associate which involved a MgGa acceptor and a N vacancy, VN.

Self-Compensation in Mg-Doped p-Type GaN grown by MOCVD. H.Obloh, K.H.Bachem, U.Kaufmann, M.Kunzer, M.Maier, A.Ramakrishnan, P.Schlotter: Journal of Crystal Growth, 1998, 195[1-4], 270-3