Defect luminescence in heavily Mg doped GaN

Behavior of the photoluminescence band at about 2.8 eV in heavily Mg doped GaN has been studied at different temperatures and excitation intensities. The 2.8 eV band is attributed to donor-acceptor transitions involving a Mg acceptor. The large blue shift of the band with increasing excitation intensity is explained by variation in the contribution of close and distant pairs to the luminescence. The red shift of the band with increasing temperature under high excitation intensity conditions results from thermal release of carriers from close pairs. The thermal activation energy of the deep donor, about 0.4 eV, is determined from the quenching of the 2.8 eV luminescence band at high temperatures.