Phonon bottleneck effects in InAs/GaInP quantum dots

The phonon bottleneck effect is studied in InAs/GaInP quantum dots (QDs). The time-resolved photoluminescence spectra from the lowest (n=1) and second lowest (n=2) exciton states in QDs are measured in the temperature range of 5–200 K. We find that the rise time of the n=1 level is about 500 ps when the excitation energy is in resonance with the n=2 level. This is a long time compared to about 200 ps in non-resonant excitation, and therefore the bottleneck effect exists between the levels n=2 and 1. In order to understand the source of the bottleneck, the temperature dependence of carrier relaxation time between the exciton levels is investigated in the assigned temperature range. With increasing temperature, the relaxation time decreases to 200 ps at 200 K. The data are in good agreement with the theoretical fit of the relaxation probability for multi-phonon processes.