Quantum-confined Stark shifts of charged exciton complexes in quantum dots

Abstract

We probe the permanent excitonic dipole of neutral and positively charged excitons in individual ${\mathrm{In}}_{0.5}{\mathrm{Ga}}_{0.5}\mathrm{As}$ self-assembled quantum dots using Stark effect perturbation spectroscopy. A systematic reduction of the permanent excitonic dipole is found as excess holes are controllably added to individual dots containing a single exciton $({X}^{0})$. Calculations of the few-body states show that this effect arises from a strong, Coulomb-mediated, spatial redistribution of the few-body wave function upon charging. By investigating correlations between the permanent dipole, polarizability, and the emission energy of ${X}^{0}$ for many dots, we also show that the strength of the $\mathrm{In}:\mathrm{Ga}$ composition gradient is related to the absolute In content.