The blue and ultra-violet photoluminescence bands of Mg-doped samples were investigated over a wide range of temperatures and excitation intensities. Red-shifts of the bands were observed with increasing temperature. The bands underwent a blue-shift with increasing excitation density. Observed shifts in the 3.2eV band were explained in terms of a potential fluctuation model for a compensated semiconductor. On the other hand, shifts in the 2.8eV band were mainly related to the saturation of luminescence from the distant donor-acceptor pairs which were responsible for this emission. Thermal quenching of the 2.8eV luminescence band was observed at high temperatures, with an activation energy of 0.3 to 0.4eV. This was attributed to the thermal release of trapped electrons from a deep donor state.

Behavior of 2.8- and 3.2eV Photoluminescence Bands in Mg-Doped GaN at Different Temperatures and Excitation Densities. M.A.Reshchikov, G.C.Yi, B.W.Wessels: Physical Review B, 1999, 59[20], 13176-83