Temperature dependence of the exciton homogeneous linewidth in In 0.60 Ga 0.40 As/GaAs self-assembled quantum dots

Single dot photoluminescence spectroscopy was used to study the homogeneous linewidth $\ensuremath{\Gamma}$ of the ground-state exciton in ${\mathrm{In}}_{0.60}{\mathrm{Ga}}_{0.40}\mathrm{As}/\mathrm{GaAs}$ quantum dots as function of temperature T. In high resolution experiments at 2 K, we find a linewidth that is limited by the excitonic lifetime corresponding to a dephasing time of almost a ns. The approximately linear increase of \ensuremath{\Gamma} with temperature up to $\ensuremath{\sim}30 \ensuremath{\mu}\mathrm{eV}$ at 60 K is considerably weaker than in structures of higher dimensionality. For higher T we observe a strong enhancement of the linewidth reaching eventually a few meV at room temperature that depends on the confined electronic shell structure.