Structural and optical characteristics of InGaN/GaN multiple quantum wells with different growth interruption

InGaN/GaN multiple quantum wells (MQWs) grown with various growth interruptions between InGaN well and GaN barrier by metalorganic chemical vapor deposition were investigated using photoluminescence, high-resolution transmission electron microscopy (HRTEM), and energy filtered transmission electron microscopy (EFTEM). The luminescence 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 blue shift. We found that the higher intensity and lower energy emission of the MQW grown without interruption is caused by the recombination of excitons localized from indium clustering regions. Evidence of indium clustering is directly observed by indium ratio map of MQWs and indium composition measurements along an InGaN well using EFTEM.