Variation of the carrier lifetime across the ground-state band of ensemble quantum dots: An indication for quantum-dot characteristics at high temperatures

High-temperature characteristics of InAs/GaAs quantum dots (QDs) with well-separated ground and excited state photoluminescence peaks were studied by time-resolved photoluminescence. The carrier lifetime across the ground state band of the ensemble QDs showed a large variation (> 2 ns) at 250 K while the lifetimes were almost the same at low temperatures. The large variation in the carrier lifetime, shorter at the high energy side and longer at the low energy side, is a clear indication of carrier transport from smaller QDs to larger QDs via the wetting layer. The variation is a good indicator to determine whether the QD characteristics are remained at high temperatures, which is important for device applications.