Temperature dependent optical properties of self-organized InAs GaAs quantum dots

We report photoluminescence (PL), time-resolved FL, and PL excitation exper iments on InAs/GaAs quantum dots (QDs) of different size as a function of t emperature. The results indicate that both the inhomogeneous properties of the ensemble and the intrinsic properties of single QDs are important in un derstanding the temperature-dependence of the optical properties. With incr easing temperature, excitons are shown to assume a local equilibrium distri bution between the localized QD states, whereas the formation of a position -independent Fermi-level is prevented by carrier-loss to the barrier domina ting thermally stimulated lateral carrier transfer. The carrier capture rat e is found to decrease with increasing temperature and, at room temperature , long escape-limited ground state lifetimes of some 10 ps are estimated. P L spectra excited resonantly in the ground state transition show matching g round state absorption and emission, indicating the intrinsic nature of exc iton recombination in the QDs. Finally, the PL excitation spectra are shown to reveal size-selectively the QD absorption, demonstrating the quantum-si ze effect of the excited state splitting.