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

Abstract

Selective excitation photoluminescence spectroscopy was employed to study InAs/GaAs self-assembled quantum dots (QDs). Under different excitation energies, different groups of QDs are selected and then 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 excitation 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 multiphonon resonance. The special joint density of state tail of the QD that extends from the wetting layer band edge facilitates carrier relaxation and is posited to explain these spectral results. (C) 2008 American Institute of Physics.