Phonon-replica transitions in InGaN/GaN quantum well structures

A side-bump feature in a photoluminescence (PL) spectrum of an InGaN compound was widely observed. With reasonable fitting to PL spectra with three Gaussian distributions, the temperature variations of the peak positions, integrated PL intensities, and peak widths of the main and first side peaks of three InGaN/GaN multiple quantum well samples with different nominal indium contents are shown and interpreted. The existence of the side peaks is attributed to phonon-replica transitions. The variations of the peak position separations and the decreasing trends of the first side peak widths beyond certain temperatures in those samples were explained with the requirement of phonon momentum condition for phonon-replica transitions. In the sample with 25% nominal indium content, the phonon-replica transition could become stronger than the direct transition of localized states.