Exciton confinement in narrow non-polar InGaN/GaN quantum wells grown on r-plane sapphire

We have investigated the optical properties of a series of non-polar InGaN/GaN single quantum wells (QWs) grown on r-plane sapphire with QW widths ranging from 7 to 45Å. The emission is attributed to recombination in regions of the QW intersected by basal plane stacking faults. For QW widths<30Å, the linewidth of both the photoluminescence (PL) spectrum and the QW exciton measured in PL excitation reduces with decreasing QW width, effects which are attributed to the increasing penetration of the exciton wavefunction into the GaN barriers. Furthermore, the associated increase in confinement energy is proposed to induce a delocalisation of the exciton within the plane of the QW/basal plane stacking fault (BSF), which results in an increased temperature sensitivity of the integrated emission intensity for QWs narrower than 22Å.