UCL-led Team Boosts Efficiency Of Quantum Light Sources With Novel Charge-Carrier Funnel

A UCL EEE-led team has developed a charge-carrier funnel structure that greatly improves the efficiency of quantum dots, and it can be used to generate single photons.

Researchers led by Professor Oleg Mitrofanov have demonstrated a novel way to make quantum dots - tiny semiconductor structures that can emit single quanta of light - significantly more efficient. The findings are presented in a pre-print of their Communications Material article, now available online.

Quantum dots are among the most promising single-photon sources for future quantum communication and computing systems. They can produce very high-quality single photons, but their overall efficiency has remained low.

To address this, researchers created a microscale three-dimensional “charge funnel” made from AlGaAs and grown by molecular beam epitaxy. This funnel guides electrons and holes towards the quantum dot, boosting its excitation efficiency by more than an order of magnitude while preserving single-photon behaviour.

They also showed that the funnel reshapes the energy landscape around the dot, enabling remote optical excitation from distances of up to 10 micrometres. This capability raises the potential for developing practical, electrically driven single-photon emitters for quantum information technologies.

Professor Mitrofanov noted that the work demonstrates how fundamental and collaborative research undertaken at UCL and in the US-based Center for Integrated Nanotechnologies (CINT) can advance next-generation quantum devices.