Ensembles of~600 AlyIn1−yAs/AlxGa1−xAs self-assembled quantum dots (QDs) are investigated using photoluminescence (PL) and time-resolved PL in the visible. At very low excitation intensities, the PL spectrum shows multiple ultranarrow luminescence lines (FWHM ~200 μeV), which are attributed to the ground-state transition of a few dots (4 or less). The temperature and intensity evolution of these sharp lines is then monitored. The temperature-dependent measurements show that the line width and lifetime of the narrow lines remain constant up to the onset of thermionic, emission. Intensity-dependent measurements show that for high excitation density the collective background, emitted by the ensemble of QDs, is enhanced relative to the amplitude of individual ultranarrow lines.
Enhancement of Optical Anisotropy by Interconnection Effect along Growth Direction in Multistacked Quantum Dots