Energy dependent carrier relaxation in self-assembled InAs/GaAs quantum dots

We performed the selective excitation photoluminescence (SEPL) spectroscopy studies on InAs/GaAs self-assembled quantum dots (QDs). Under different excitation energies, different groups of QDs are selected and emit light. The excited carriers relax to the ground state through different mechanisms when excited at different energies. Three distinct regions with different mechanisms in carrier excitations and relaxation are identified in the emission spectra. These three regions can be categorized, from high energy to low energy, as continuum absorption, electronic state excitation, and multi-phonon resonance. The QDs special joint density-of-state tail extending from the wetting layer peak facilitates the carrier relaxation and was suggested to explain these spectral results. (c) 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.