Fine structure of highly charged quantum dot excitons: turning dark into bright states

Abstract

The emission of a neutral exciton in a symmetric semiconductor quantum dot is split by the isotropic electron–hole exchange interaction into dark and bright states. We demonstrate that for a doubly charged exciton, there are also two states split by the electron–hole exchange, but both states are now bright. We also uncover a fine structure in the emission from the triply charged exciton, the singly and doubly charged biexcitons. By measuring these splittings we can access the isotropic exchange energies for holes in the ground and electrons ground and excited states.