Time-resolved photoluminescence cross-correlation measurements on InAs quantum dots

We have studied recombination and relaxation dynamics in InAs quantum dots by means of photoluminescence cross-correlation techniques with sub-picosecond time-resolution. We have determined the relative radiative efficiencies for carrier recombination from different energy levels of the quantum dots and show that the radiative efficiency decreases with increasing transition energy, indicating that carrier access to non-radiative recombination centres increases for higher-energy states inside the dots. Cross-correlation measurements with both excitation beams of the same circular polarization and with the beams having opposite circular polarization are shown to give direct insight into the spin relaxation dynamics in the quantum dots and the wetting layer.