Photoluminescence dynamics in highly nonhomogeneously excited GaN

The analysis of the room-temperature photoluminescence (PL) dynamics in GaN 4.5-mu m-thick layers under different excitation intensities revealed nonexponentional PL decay with the fast and slow transients. The fast decay is clearly resolved under lower excitation (< 100 MW/cm(2)) and high excitation (>100 MW/cm(2)). Theoretical modeling and comparison of the calculated results with the experimental data showed that the observed PL behavior is determined by the space nonhomogeneity of carriers generated by strongly absorbed 25 ps duration laser pulse, the diffusion processes, as well as by the surface recombination. The latter mechanism plays an important role in the PL decay at lower excitation intensities, whereas the surface recombination saturates at high excitation levels. The radiative bimolecular recombination along with the stimulated emission predominates under these circumstances. The extracted carrier parameters are in good agreement with the values measured using other techniques.