Few-particle interactions in charged ${\mathrm{In}}_x{\mathrm{Ga}}_{1\mathrm{-}x}\mathrm{As}/\mathrm{GaAs}$ quantum dots

The impact of few-particle interactions on excited states of excitons localized in self-organized ${\mathrm{In}}_x{\mathrm{Ga}}_{1-x}\mathrm{As}/\mathrm{GaAs}$ quantum dots (QD’s), charged either with electrons or holes, is investigated. Excited-state absorption is probed size selectively by photoluminescence excitation spectroscopy improving the achieved resolution beyond the inhomogeneous broadening. Charging QD’s embedded in suitable diode structures leads to nonlinear changes of the absorption characteristics for the individual excited-state transitions, enabling their unambiguous identification. Few-particle interactions lead to a renormalization of the excited-state transition energies, which ranges from a pronounced red shift to a blue shift depending on the excited-state transition and the type of spectator charge. The most pronounced effects occur charging the ground state of the QD’s. The results are supported by eight-band $\mathbf{k}\cdot \mathbf{p}$ model calculations using a configuration-interaction scheme to account for the Coulomb interaction in the few-particle states.