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Time-resolved photoluminescence (PL) from InAs/GaAs quantum dots with a bimodal size distribution is used to investigate the dynamic carrier-transfer processes which couple transfer between similarly sized quantum dots and between quantum dots in different size categories. The relationship between the decay time and the emission energy appears staircaselike and the energetic positions of the steps as well as the shape can be correlated to the shape of the steady-state PL emission through a rate-equation theory. These results show how transient PL can be used to investigate the dynamics of carrier transfer in quantum-dot systems.

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Photoluminescence (PL) spectra and time-resolved PL data from AlGaAs/GaAs superlattice structures containing thin InAs layers of about 1–3 monolayer grown on semi-insulating (001)-oriented GaAs substrates at lowered temperatures are studied. The size distribution of InAs quantum dots (QDs) among different families (modes) is controlled by variation of growth temperature and/or growth interruption. We demonstrate the stabilization of the PL magnitude caused by strong coupling between different modes and the full width at half maximum of “large size” QD modes within a certain temperature interval (50–150 K) due to feeding of the radiative transitions from nonradiative decay and carrier transfer arising from decaying excitonic states of the small size QD modes. Strong competition between different channels of ground state relaxation leads to an oscillating dependence of the PL transient for the small size QD mode. Efficient inter- and intramode tunneling rules out “bottleneck restrictions” for the PL. The parameters of intra- and intermode tunneling are determined from time-resolved PL.

InAs quantum dots grown in a GaAs matrix are investigated using capacitive transient spectroscopy and transmission electron microscopy (TEM). Two deep levels are detected which are energetically too deep to be the intrinsic electron levels of the quantum dots. Both TEM as well as the detailed non-exponential behavior of the electron capture indicate that the traps do not result from dislocations in the GaAs matrix. We propose that the measured trap levels are due to point defects in or near the quantum dots.