Threshold of stimulated emission in GaN layers grown by various techniques

Room-temperature luminescence properties of dense electron-hole plasma were studied in GaN epilayers grown by various techniques (by LUMILOG grown on sapphire substrate, by AIXTRON via a MOCVD reactor grown on SiO and by UNIPRESS by the MOCVD technique grown on sapphire). By studying emission properties of plasma in lateral “thin stripe” excitation geometry the values of the threshold of the stimulated emission were estimated. A linear decrease of the stimulated emission threshold with a decrease in the density of the dislocations in GaN layers was observed. This dependence was shown to be mainly contributed by a decrease in carrier lifetime, while the impact of variation in carrier diffusion coefficient was found to be minor. Incorporation of iron into GaN layer significantly increased the stimulated emission threshold. The role of the light-scattering losses on the values of the stimulated emission threshold was discussed.