Evolution of the energy levels in quantum dot ensembles with different densities

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Abstract
Ensembles of self-assembled InAs/GaAs quantum dots (QDs) have been obtained with different densities by molecular beam epitaxy. The evolution of the structural and optical properties with coverage shows that lateral interactions are present for QD spacings of hundreds of nanometers (coverage>∼109 QDs/cm2). Clear evidence for transfer of InAs from the wetting layer to the QDs is observed at the onset of the Stranski–Krastanow’s island formation for 1.83 monolayers (MLs). QDs with sharp electronic shell structures are observed by state-filling spectroscopy for the low density ensembles (1.83–1.91 ML). A decrease in the photoluminescence intensity is observed for more than 1.96 ML and is associated with the coalescence of the islands.