Long luminescence lifetime in self-assembled InGaAs/GaAs quantum dots at room temperature

Time-resolved photoluminescence (PL) measurements of high-quality self-assembled small $In0.5Ga0.5As/GaAs$ quantum dots (QDs) show that the PL decay time of the QD ground state transition is nearly constant when the temperature is below 80 K and increases monotonously from 1.0 to 5.5 ns when the temperature increases from 80 to 300 K. The increased radiative lifetime of the QD ground state at higher temperatures is attributed to the thermal population of the subwetting-layer continuum states and could be one of the fundamental reasons for the low modal gain of the QD ground state transition in single-layer self-assembled QD lasers.