We have succeeded in preparing excitons with a specific charge in single semiconductor quantum rings. Buried InAs quantum rings are loaded with electrons from a reservoir through a tunneling barrier and an additional electron–hole pair is generated by optical excitation. Single rings are addressed with nano-optical techniques. We observe abrupt shifts in the emission energy as electrons are added one by one. Furthermore, the experiments provide unique insights into the interaction of electrons in semiconductor nano-islands with their environment.

We would like to thank J.P. Kotthaus for stimulating discussions. This work was funded by the DFG (Project SFB 348) and by QUEST, a NSF Science and Technology Center.

7 páginas, 5 figuras.

Peer reviewed