Linewidth statistics of single InGaAs quantum dot photoluminescence lines

Abstract

We have used photoluminescence spectroscopy with high spatial and spectral resolution to measure the linewidths of single emission lines from In0.5Ga0.5 As/GaAs self-assembled quantum dots. At 10 K, we find a broad, asymmetric distribution of linewidths with a maximum at 50 μeV. The distribution of linewidths is not significantly influenced by small variations in the quantum dot confinement potential. We claim that the wider transition lines are broadened by local electric field fluctuations while narrower lines are homogeneously broadened by acoustic-phonon interactions. The width of narrow single-dot luminescence lines depends only weakly on temperature up to 50 K, showing a broadening of 0.4 μeV/K. Above 50 K, a thermally activated behavior of the linewidth is observed. This temperature dependence is consistent with the discrete energy level structure of the dots.