Unusual temperature-dependent optical properties of self-organized InAs/GaAs quantum dots at high excitation power

The temperature-dependent photoluminescence (PL) properties of InAs/GaAs self-organized quantum dots (QDs) have been investigated at high excitation power. The fast redshift of the ground-state and the first excited-state PL energy with increasing temperature was observed. The temperature-dependent linewidth of the QD ground state with high carrier density is different from that with low carrier density. Furthermore, we observed an increasing PL intensity of the first excited state of QDs with respect to that of the ground state and demonstrate a local equilibrium distribution of carriers between the ground state and the first excited state for the QD ensemble at high temperature (T > 80 K). These results provide evidence for the slowdown of carrier relaxation from the first excited state to the ground state in InAs/GaAs quantum dots.