Carrier dynamics of high-efficiency green light emission in graded-indium-content InGaN/GaN quantum wells: An important role of effective carrier transfer

Optical properties and carrier dynamics of high-efficiency green-light-emitting InGaN/GaN multiple quantum wells (MQWs) with graded-In-content were studied by photoluminescence (PL), PL excitation, and time-resolved PL techniques. Two separated InGaN-related peaks were clearly found in PL spectra due to strong phase separation in the well of the graded-In-content InGaN MQWs. The integrated intensity of the main InGaN green emission (∼510 nm) decreased by only about a factor of 7 with increasing temperature from 10 to 300 K, indicating strong carrier localization and high quantum efficiency. Strong carrier transfer from low-In-content region with weak carrier localization to high-In-content part with strong carrier localization was observed by time-resolved PL. Therefore, we conclude that the effective carrier transfer from weakly to strongly localized states plays an important role to enhance brightness and quantum efficiency in the green-light-emitting InGaN MQWs with graded-In content.