Dual contribution to the Stokes shift in InGaN-GaN quantum wells

By comparing photoluminescence and photo reflectance spectra taken on a ser ies of InGaN-GaN quantum wells grown under identical conditions except the growth time of the InGaN layers, we could monitor the Quantum Confined Star k Effect (QCSE) without changing the nanotexture of the alloy layers. Our r esults indicate that, for quantum wells which radiate in the red, the contr ibution of the QCSE superimposes on the intrinsic localization phenomena of the carriers in the InGaN alloy. and is larger by one order of magnitude. Interpretation of data for samples that emit from the blue to the red can p rovide only partial conclusions if both localization effects and QCSE are n ot taken into consideration.