Effect of growth interruptions on the light emission and indium clustering of InGaN/GaN multiple quantum wells

InGaN/GaN multiple quantum wells (MQWs) grown with various growth interruptions between the In_xGa_1-xN well and GaN barrier by metalorganic chemical vapor deposition were investigated using photoluminescence (PL), high-resolution transmission electron microscopy, and energy filtered transmission electron microscopy (EFTEM). The integrated PL intensity of the MQWs with growth interruptions is abruptly reduced compared to that of the MQW without growth interruption. Also, as the interruption time increases the peak emission shows a continuous blueshift. Evidence of indium clustering is directly observed both by using an indium ratio map of the MQWs and from indium composition measurements along an InGaN well using EFTEM. The higher-intensity and lower-energy emission of light from the MQW grown without interruption showing indium clustering is believed to be caused by the recombination of excitons localized in indium clustering regions and the increased indium composition in these recombination centers.