EFFECT OF CARRIER EMISSION AND RETRAPPING ON LUMINESCENCE TIME DECAYSIN INAS GAAS QUANTUM DOTS/

We report time-resolved photoluminescence measurements as a function o f temperature for InAs quantum dots grown by molecular-beam epitaxy on GaAs(100). As the temperature is increased, the decays on the high-en ergy side of the photoluminescence band speed up, while the decay time s on the low-energy side of the band increase. This increase occurs up to a ''drop'' temperature, which increases with decreasing emission e nergy, beyond which the decay times decrease. We present a coupled rat e-equation model which includes the effects of thermal emission from q uantum dot states into the wetting layer followed by transport and rec apture, which reproduces the dispersive temperature dependence observe d. The activation energy for thermal emission from quantum dots emitti ng at a given frequency is found to be approximately one-half the effe ctive band-gap difference between the quantum dot and the wetting laye r. This result is consistent with detailed balance requirements under the assumption that, on average, electrons and holes are captured and emitted by quantum dots in pairs.