Slow Carrier Relaxation among Sublevels in Annealed Self-Formed InGaAs/GaAs Quantum Dots

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Abstract
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°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 (≈10-10 s) and the recombination lifetimes (≈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.