Near-field photoluminescence study of InAs/AlGaAs quantum-dot-based nanoclusters: band filling effect

We have performed near-field spectroscopy and microscopy of the InAs/AlGaAs quantum-dot-based nanoclusters. It is observed that the photoluminescence spectra of spatially confined excitons in the nanoclusters is blue-shifted up to 20 meV as the power density is increased. In particular, the near-field photoluminescence images have shown that excitons became spatially confined gradually from lower energy state (1.4150 eV) to higher energy state (1.4392 eV) as the excitation power is increased, which is indicative of the band-filling effect of semiconductor nanostructures.