Ultrahigh-density self-assembled quantum dots of InGaAs and suppression of optical state-filling effect

We have grown ultrahigh-density self-assembled quantum dots (QDs) of InGaAs with sheet densities up to 2.5×1011 cm-2 and lateral diameters down to 10 nm, where the dot density increases with increasing As pressure during dot growth under optimum growth conditions. A ground-state photoluminescence (PL) spectrum shows a spectral width of 47 meV for the highest-density sample. Optical excitation-density dependences of the PL intensity and time profile are studied. The PL intensity from QD excited states increases with increasing excitation power, originating from a state-filling effect in QDs, which is directly confirmed by a plateau-like behavior on the PL decay curve. We find that the filling effect is significantly suppressed in the above ultrahigh-density dot ensemble, which suggests potential applications to superior energy-saving lasing and spin-functional optical devices.