Temperature Induced Anomalous Exciton Localization in InGaN/GaN and GaN/AlInN Multiple Quantum Wells

Abstract

InGaN and AlInN alloys including their relevant Quantum Well (QW) structures have attracted intensive research interest due to their potential applications in numerous optoelectronic devices. However, the emission mechanism in such QWs is still unveiled incompletely. The physical origin of spontaneous emission in InGaN/GaN or GaN/AlInN QWs is attributed to the recombination of localized excitons. The localization of exciton occurs due to the formation of Indium-rich clustering and abrupt interfaces between well and barrier layers. Conversely, the InGaN/GaN QWs can be grown without Indium-rich clustering and abrupt interfaces. Thus a detail understanding is essential to link the intricate structure of InGaN/GaN and GaN/AlInN QWs with their secretive optical behaviors. In this dissertation, the details of exciton localization dynamics in InGaN/GaN and GaN/AlInN multiple quantum wells (MQWs) have been reported using Monte Carlo simulation of exciton hopping for a wide range of temperature of 10K to 300K. The calculated photoluminescence (PL) peak energy position of both of MQWs shows unusual behavior (redshift-blueshift-redshift) with the increase in temperature. The PL line width also exhibits W-shaped temperature dependent inhomogeneity. It is found that the phononinduced lifetime variation of excitons have the remarkable effects on the PL peak position and line-widths in both of MQWs. The blue-shift of PL peak position is observed at high temperature in the MQWs with well and barrier thicknesses near the critical values, indicating the dominancy of two dimensional excitonic kinetics for the entire range of temperature. vi Significantly, different temperature dependences for PL line-widths were perceived for the GaN/AlInN MQWs with different barrier heights. The MQWs having barrier height near to the lattice matched QW structure of GaN/AlInN showed the smaller band potential profile fluctuation. These results could be important to understand the emission properties of InGaN and AlInN MQWs optoelectronic devices.