Effect of spectral broadening and electron-hole scattering on carrier relaxation in GaAs quantum dots

Luminescence efficiency in quantum dots has been a matter of some controversy recently. Theoretically, poor efficiency has been predicted owing to the phonon bottleneck in carrier relaxation, while slightly enhanced luminescence has been reported in several experiments. The approach of this letter differs from previous theoretical work in that the scattering rates are computed self-consistently accounting for the spectral broadening of the electronic spectra due to a finite energy level lifetime. Scattering of electrons and holes confined in the dot is found to be responsible for breaking the phonon bottleneck in electron relaxation reducing the relaxation time from several ns to several hundred ps. Results of a Monte Carlo simulation also including confined and interface polar optical phonon and acoustic phonon scattering for a range of quantum dot dimensions and temperatures are presented. These results may provide an explanation of the absence of a significant reduction in quantum dot luminescence compared with that from quantum wells.