Abstract
Excited states and energy relaxation processes are studied for self-organized InAs/GaAs quantum dots (QDs). Photoluminescence excitation (PLE) spectra show sample-dependent either multi-LO-phonon resonances or excited state transitions, revealing the dominant carrier relaxation mechanism or the size-dependent excited state splitting of the QDs, respectively. Time-resolved photoluminescence results indicate sample-dependent non-radiative recombination, suggesting a model for the observed PLE behavior, analogous to hot carrier relaxation in higher-dimensional systems. Carrier relaxation in the self-organized InAs/GaAs QDs proceeds by multi-LO-phonon scattering on a 40 ps time scale, which is short compared to radiative (>500 ps) and non-radiative (>100 ps) recombination times, accounting for the absence of a phonon bottleneck effect in PL spectra. However, carrier relaxation might effect the stimulated emission region.
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