Bimodal luminescence behavior of spatially-ordered seven-stacked InAs/InAlGaAs quantum dots

Seven-stacked InAs/InAlGaAs quantum dots (QDs) grown on InP substrates have been studied using photoluminescence (PL) and time-resolved PL techniques, and the results show a bimodal luminescence behavior. The seven-stacked QD sample shows a redshifted PL emission energy, a broad PL linewidth, and a strong temperature dependent PL compared with the single layer QD sample. The decrease of the PL decay time with increasing emission wavelength has been observed in the seven-stacked sample, but not in the single layer sample. All of these results are attributed to the bimodal size distribution of QDs in the seven-stacked sample, which originates from different sizes of spatially ordered QDs formed on different layers.