RADIATIVE LIFETIME OF LOCALIZED EXCITONS IN GAAS QUANTUM DOTS

We have investigated the exciton radiative lifetime in GaAs quantum dots fabricated by metal organic chemical vapor selective growth technique. The radiative lifetime tau(r) can be obtained from the results of photoluminescence(PL) and time-resolved PL measurements. At low temperature below 30 K, tau(r) is almost constant (similar to 450 psec) and longer than that in quantum wells. This result can be explained by reduced exciton coherence volume with the change of the dimensionality of confinement. The increase of tau(r) above 30 K results from the contribution of higher sub-levels. By considering the thermal energy at 30 K, effective lateral size of quantum dots can be estimated as similar to 80 nm x 80 nm, which is smaller than the size determined by SEM observation.