Lasing mechanism of InGaN-GaN-AlGaN MQW laser diode grown on SiC by low-pressure metal-organic vapor phase epitaxy

We studied the lasing mechanism of an InGaN-GaN-AlGaN multiquantum-well (MQW) laser diode by making various optical characterizations on the diode. Excitation power dependence of photoluminescence (PL) intensity was obtained to investigate the carrier recombination process of the laser. Surface emission and edge emission were compared by optical pumping to clarify where the lasing lines were located in relation to the absorption continuum. From the results, we demonstrate that lasing phenomena in our laser are dominated by free carriers. PL mapping was also taken on the same laser chip to examine the in-cavity bandgap inhomogeneity. We found a very large bandgap scattering of 100 meV. We also found that the wavelength distribution has a periodic modulation. We clarified that the various stimulated emission lines observed in our lasers are caused by the in-cavity spatial bandgap inhomogeneity of the InGaN MQW.