Efficient single-photon emission via quantum-confined charge funneling to quantum dots

Quantum light sources, particularly single-photon emitters (SPEs), are critical for quantum communications and computing. Among them, III-V semiconductor quantum dots (QDs) have demonstrated superior SPE metrics, including near-unity brightness, high photon purity, and indistinguishability, making them especially suitable for quantum applications. However, their overall quantum efficiency — determined by a product of the internal, excitation, and out-coupling efficiencies — remains limited, primarily due to low (typically below 0.1%) excitation efficiency. This has hindered their applications in quantum information systems, including for multi-photon cluster state generation and Boson sampling. To mitigate the low excitation efficiency, here we realized liquid droplet etched GaAs QDs in a microscale 3D AlGaAs charge-carrier funnel using molecular beam epitaxy. The funnel channels charge carriers to the QD and enhances the overall emission efficiency by over one order of magnitude while preserving the SPE behavior. We reveal that a modified energy landscape around the QD leads to the excitation efficiency improvement. These energy landscape-modified QDs can be operated with optical excitation up to 10 µm away from the QD, raising the promise of efficient and scalable electrically driven epitaxial QD SPE for quantum information systems.