Optical characterization of quaternary AlInGaN epilayer and multiple quantum wells grown by a pulsed metalorganic chemical vapor deposition

The optical properties of quaternary AlInGaN epilayers and AlInGaN/AlInGaN multiple quantum wells (MQWs) grown by a pulsed metalorganic chemical vapor deposition have been investigated by means of photoluminescence (PL) and time-resolved PL measurements. The PL emission peaks in both AlInGaN epilayers and MQWs show a blueshift with increasing excitation power density. The PL intensities of MQWs are much stronger (∼3-4 times) than that of the epilayer. The PL emission intensities (I_emi) of both AlInGaN epilayers and MQW samples increase superlinearly with increasing excitation power density (I_exc), following a power-law form, I_emi I_exc^β. The PL decay times of MQWs are longer than that of epilayer. The longer PL decay times may be due to a stronger localization effect of carriers/excitons at band tail states and wave function separation caused by the quantum confined Stark effect. These results indicate that AlInGaN/AlInGaN MQWs grown by a PMOCVD are promising materials for ultraviolet light emitting diode (LED) applications similar to the InGaN/InGaN system for blue LED applications.