“…In the same doping range, two phenomena occur: the photoluminescence spectra of the samples begin to be dominated by an intense and broad blue band, peaking in the 2.7-2.9 eV range, and the free hole concentration begins to drop with increasing doping (auto-compensation). Based on the fact that, at inversion domain boundaries, an interfacial charge with superficial density twice the GaN spontaneous polarization (2 Â 0.029 C/m 2 ) exists, we have already shown, that the localization of minority electrons in the wells formed by the IDB-induced electric field discontinuities is sufficient to account for the energetic position of this blue luminescence band, and its variation with defect size [10]. In the following, we shall focus on the auto-compensation problem.…”