Luminescence Intensity Reduction in Mg-Doped GaN Grown by Metalorganic Chemical Vapor Phase Epitaxy

Photoluminescence dynamic responses of a heavily Mg-doped GaN grown by metalorganic chemical vapor phase epitaxy have been investigated. As the probe power density increased from 2.5 to 925 W/cm2, a Mg-related emission band shifted from 2.82 to 3.16 eV revealing characteristics of donor-acceptor pair recombination. The intensity evolution also showed slow decay that suggests the metastable emission behavior. A simple potential barrier model was proposed to occur between the Mg related deep levels and common Mg acceptor level, which impedes electron relaxation and thus slows down the luminescence decay. From the variation of decay time constant with temperature, a barrier energy was deduced to be about 69 meV which is very close to the electrical result of 68 meV.