Researchers from the Graphene Flagship have used layered materials including graphene, boron nitride and a transition metal dichalcogenide (TMD) to create all electrical quantum LEDs which can emit single photons. The devices are said to have the potential to act as on-chip photon sources in quantum information applications.
The LEDs are made of thin layers of different materials, stacked to form a heterostructure. Electrical current is injected into the device, tunnelling from single layer graphene, through a tunnel barrier of a few layers of boron nitride and into a mono- or bilayer of a transition metal dichalcogenide (TMD), such as tungsten diselenide (WSe2). In this layer, electrons recombine with holes to emit single photons.Previously, single photon generation was said to rely on optical excitation, large scale optical setups with lasers and precise alignment of optical components.
Researchers from the University of Cambridge explained that “In a scalable circuit, we need fully integrated devices that we can control by electrical impulses, instead of a laser that focuses on different segments of an integrated circuit. For quantum communication with single photons, and quantum networks between different nodes – for example, to couple qubits – we want to be able to just drive current and get light out. There are many emitters that are optically excitable, but only a handful are driven electrically.”
The team added that, in its devices, a current of less than 1µA ensured that single photon behavior dominated the emission characteristics.