Optical properties of InGaN/GaN MQWs were studied by PL and Raman measurements.
Inserting a QSL underlying buffer layer can release strain in the MQWs.
The strain release reduces QCSE in the InGaN well layers.
The strain release facilitates composition fluctuation of the InGaN well layers.
The strain release enhances radiative recombination rate of the MQWs.