Photoluminescence of Mg-doped GaN with Different Mg Concentrations After Annealing at Different Temperatures

The blue band (BB) in low temperature photoluminescence of Mg-doped GaN films with different Mg concentrations is investigated. The BB peak of as-grown samples with higher Mg concentration centers at lower energy. A shift of the BB peak energy is observed after annealing in N₂ at different temperatures. Meanwhile, the difference between the BB peak energies diminishes for raised annealing temperature, and the BB peaks for different samples converge to 2.92 eV after annealing at 850 °C. These experimental results can be accounted for by a model based on compensation effect. The shift of BB lines provides a useful criterion for the optimum annealing temperature of the Mg-doped GaN material, and the value is taken to be 850 °C in our case.