Quantised Charge Transport driven by a Surface Acoustic Wave in induced unipolar and bipolar junctions

TL;DR

This paper demonstrates quantised charge transport driven by surface acoustic waves in undoped GaAs/AlGaAs heterostructures, enabling single-electron and electron-hole current control with potential applications in quantum information processing.

Contribution

It introduces a novel method for creating lateral p-n junctions in undoped heterostructures and demonstrates SAW-driven quantised electron transport and light emission at these junctions.

Findings

SAW-driven single-electron quantised current observed

Electrons pumped across induced p-n junctions with light emission

Potential for quantised electron-to-hole current and single-photon emission

Abstract

Surface acoustic waves (SAWs) have been used to transport single electrons across long distances of several hundreds of microns. They can potentially be instrumental in the implementation of scalable quantum processors and quantum repeaters, by facilitating interaction between distant qubits. While most of the work thus far has focused on SAW devices in doped GaAs/AlGaAs heterostructures, we have developed a method of creating lateral p-n junctions in an undoped heterostructure containing a quantum well, with the expected advantages of having reduced charge noise and increased spin-coherence lifetimes due to the lack of dopant scattering centres. We present experimental observations of SAW-driven single-electron quantised current in an undoped GaAs/AlGaAs heterostructure, where single electrons were transported between regions of induced electrons. We also demonstrate pumping of electrons by a SAW across the sub-micron depleted channel between regions of electrons and holes, and observe light emission at such a lateral p-n junction. Improving the lateral confinement in the junction should make it possible to produce a quantised electron-to-hole current and hence SAW-driven emission of single photons.