Tunneling blockade and single-photon emission in GaAs double quantum wells

TL;DR

This paper demonstrates how tunneling blockade in GaAs double quantum wells enables single-photon emission from impurity-bound excitons, with potential applications in quantum communication.

Contribution

It reveals the role of intra-QW charged excitons in blocking tunneling and highlights impurity-bound excitons as stable single-photon sources.

Findings

Tunneling blockade creates a gap in indirect exciton emission.

Impurity-bound excitons exhibit anti-bunched photon emission.

Emission energies are narrowly distributed (~10 meV).

Abstract

We report on the selective excitation of single impurity-bound exciton states in a GaAs double quantum well (DQW). The structure consists of two quantum wells (QWs) coupled by a thin tunnel barrier. The DQW is subject to a transverse electric field to create spatially indirect inter-QW excitons with electrons and holes located in different QWs. We show that the presence of intra-QW charged excitons (trions) blocks carrier tunneling across the barrier to form indirect excitons, thus opening a gap in their emission spectrum. This behavior is attributed to the low binding energy of the trions. Within the tunneling blockade regime, emission becomes dominated by processes involving excitons bound to single shallow impurities, which behave as two-level centers activated by resonant tunneling. The quantum nature of the emission is confirmed by the anti-bunched photon emission statistics. The narrow distribution of emission energies ($\sim 10$~meV) and the electrical connection to the QWs make these single-exciton centers interesting candidates for applications in single-photon sources.