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 stag es of processing at room temperature. The photoluminescence kinetics are we ll described by a stretched exponential exp[-(t/tau)(beta)], indicating sig nificant disorder in the material. We attribute the disorder to nanoscale q uantum 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 ins ide the two-dimensional quantum well. The time-resolved photoluminescence f rom a LED wafer, before the final stages of processing, suggests the import ance of quantum dots of high indium concentration on the LED operation. (C) 1999 American Institute of Physics. [S0021-8979(99)01514-5].