Time-resolved photoluminescence measurements of quantum dots in InGaN multiple quantum wells and light-emitting diodes

We have used time-resolved photoluminescence to examine InGaN/GaN multiple quantum wells (MQWs) and light-emitting diodes (LEDs) before the final stages of processing at room temperature. The photoluminescence kinetics are well described by a stretched exponential exp[-(t/tau)(beta)], indicating significant disorder in the material. We attribute the disorder to nanoscale quantum dots of high local indium concentration. For the three MQWs examined, the stretching parameter beta and the stretched exponential lifetime tau were found to vary with emission energy. The stretching parameter beta for the emission peak of the three MQWs was observed to increase from 0.75 to 0.85 with apparently increasing indium phase segregation. A higher degree of indium phase segregation is consistent with more isolated quantum dots inside the two-dimensional quantum well. The time-resolved photoluminescence from a LED wafer, before the final stages of processing, suggests the importance of quantum dots of high indium concentration on the LED operation. (C) 1999 American Institute of Physics. [S0021-8979(99)01514-5].