Optically detected magnetic resonance of the red and near-infrared luminescence in Mg-doped GaN

We report photoluminescence (PL) and optically detected magnetic resonance (ODMR) measurements on magnesium-doped GaN samples grown by metal-organic chemical vapor deposition, molecular beam epitaxy, and high-pressure-high-temperature synthesis. The samples exhibit at least three luminescence bands in the red-to-infrared spectral range with maxima at approximate to1.75, approximate to1.55, and below 1.4 eV. ODMR on these emission bands reveals two deep defects with isotropic g values of 2.001 and 2.006 and linewidths of 4-5 and 18-32 mT, respectively. Spectrally resolved ODMR experiments suggest that a donor-to-deep defect recombination is responsible for the transitions at 1.75 eV, while an acceptor-to-deep defect transition causes the PL bands with lower energy. The deep centers involved are attributed to defects with energy levels in the lower part of the band gap but close to the midgap region.