Slow carrier relaxation among sublevels in annealed self-formed InGaAs/GaAs quantum dots

Slow carrier relaxation among discrete sublevels in self-formed InGaAs/GaAs quantum dots was studied by means of photoluminescence (PL) and time-resolved photoluminescence spectroscopy before and after annealing. The PL intensity of the ground level drastically decreased after annealing at above 600 degrees C, while that of the second level was not much influenced, suggesting a delicate balance between carrier relaxation and recombination among sublevels. We propose a model to describe the decay process of the number of carriers in an uncoupled dot ensemble, and determine the carrier relaxation lifetimes (approximate to 10(-10) s) and the recombination lifetimes (approximate to 10(-9) s) of sublevels in annealed samples by time-resolved measurements. Simulation with the measured lifetimes adequately explained the change of PL spectra after annealing.