We report systematic temperature-dependent measurements of photoluminescence spectra in self-assembled InGaAs/GaAs quantum rings (QRs) under resonant excitation condition. We have studied the rise in temperature of the ground-state intensity. The carrier transfer between the ground state of the small ring family towards the big-ring family of the bimodal size distribution is identified by analyzing the photoluminescence spectra. This effect is observed in very thin spacer and under resonant excitation. This situation makes important the lateral tunneling of excitons between rings under low temperatures (10 K). Tunneling time about 1ns was estimated at low temperature and compared to similar carrier transfer in quantum dots (QDs) found in the literature.
International audienceIn pump-probe experiments, we measured the anisotropic exchange energy splitting of the low-lying electron-hole pair states in an ensemble of as-grown InAs/GaAs self-assembled quantum dots. This splitting shows a monotonic decrease with the energy of interband emission. We discuss this result considering different parameters: shape anisotropy, wavefunction confinement, size of the quantum dots, and piezoelectric effect. (c) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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