Behavior of 2.8- and 3.2-eV photoluminescence bands in Mg-doped GaN at different temperatures and excitation densities

Abstract

The blue and ultraviolet photoluminescence bands in Mg-doped GaN have been investigated over a wide range of temperatures and excitation intensities. Redshifts of the bands were observed with increasing temperature. The bands underwent a blueshift with increased excitation density. The observed shifts of the 3.2 eV band are explained by a potential fluctuation model for a compensated semiconductor. In contrast, the shifts of the 2.8 eV band are essentially related to saturation of luminescence from distant donor-acceptor pairs responsible for this emission. Thermal quenching of the 2.8 eV luminescence band was observed at high temperatures with an activation energy of 0.3--0.4 eV. It is attributed to thermal release of trapped electrons from a deep donor state.