Effects of carrier localization on the optical characteristics of MOCVD-grown InGaN/GaN heterostructures

We have studied both the spontaneous and stimulated emission (SE) propertie s as a function of excitation photon energy for InGaN/GaN multiple quantum wells (MQWs). A significant redshift of the SE peak with decreasing excitat ion photon energy was observed as the excitation photon energy was tuned be low a certain photon energy ("mobility edge") for the InGaN/GaN MQWs, with similar behavior observed for the spontaneous emission. The relative positi on of the mobility edge with respect to the absorption edge and the spontan eous and stimulated emission peak positions indicates the emission originat es from carriers localized by extremely large potential fluctuations in the InGaN active layers of the MQWs. Therefore, carrier localization in the In GaN active regions explains the observed spontaneous and stimulated emissio n behaviors of these materials.