Photoluminescence of single InGaN quantum dots grown at low surface densities by MOVPE

We report the observation of photoluminescence due to single InGaN dots using samples containing very low surface dot densities. InGaN dot samples were grown by metalorganic vapour phase epitaxy with varying surface dot densities, the lowest being below 1 per μm². The dots are typically 30-40 nm in diameter and 4-6 nm in height. Photoluminescence spectra taken from large dot ensembles indicate a low energy tale to the InGaN layer emission, which increases in intensity as the dot density increases. The energy resolved photoluminescence lifetime indicates that low energy feature is long lived, a significant rise time for the low energy photoluminescence also indicates slow carrier relaxation. The use of 400 nm apertures in aluminium shadow masks allows the observation of sharp line features due to individual exciton localisation centres. Under low excitation powers the broadband InGaN epilayer emission is found to break up into very large number of sharp line features consistent with the presence of strong localisation excitons within the InGaN epilayer due to alloy fluctuations. In addition, on the low energy wing of the quantum well band, strong, isolated sharp emission lines are observed. Many such apertures containing single line emission spectra have been observed.