A Potential Single-Photon Source Driven by a Surface Acoustic Wave

Quantum cryptography requires a high-rate, true single-photon source in order to attain guaranteed security, while photon-based qubits offer the advantage of compatibility with quantum communication frameworks. We have developed a method of creating lateral p-n junctions in undoped GaAs wafers capable of producing single photons using a surface acoustic wave (SAW). In a piezoelectric material, a SAW consists of both an electrostatic potential and an elastic wave travelling parallel to the surface. A SAW can drag a stream of single electrons along a narrow channel to produce a quantised current. We have extended this technique to drag electrons into a region of holes at the end of the channel, where each electron recombines with a hole and emits a photon. In order to achieve a single-photon source, we have developed techniques for inducing both electrons and holes in close proximity on the same chip. This made it possible to demonstrate SAW-driven acoustoelectric current across an n-i-n, p-i-p, and finally an n-i-p junction device. Moreover, quantisation of the SAW-driven current is achieved for the n-i-n junction device by modulating the side gates to confine the carriers to a 1D channel across the junction.