Multiexcitonic emission from single elongated InGaAs/GaAs quantum dots

In this work, we present both experimental data and simulations of multiexcitonic emission spectra of single self-assembled elongated In0.3Ga0.7As/GaAs quantum dots. The emission spectra reveal an unusual evolution with the increased excitation power density. First, a biexciton line appears simultaneously with its low energy sideband, the origin of which has already been postulated previously and related to the interaction of a quantum dot biexciton with excitons generated in the surrounding wetting layer. A further increase of the excitation causes a disappearance of the exciton line accompanied with a transformation of the biexciton sharp line and its sideband into a redshifting broad emission band. The latter recalls a typical feature of the transition from excitonic emission into electron-hole plasma called Mott transition, which is possible to occur in wire-like structures under the conditions of very high carrier densities. However, we propose an alternative explanation and show that this behavior can be well explained based on a multilevel rate equation model, indicating that such a dependence of the emission spectra is a fingerprint of a formation of multiexcitonic states. Further, we discuss the importance of various quantum system parameters as the radiative lifetimes or spectral linewidths. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3695458]