GaSb/GaAs quantum ring single photon LEDs (QR_SPLEDs)

Lead Research Organisation: Lancaster University
Department Name: Physics


Quantum technologies exploit the exotic properties of nature described by quantum mechanics to deliver devices with unprecedented speed, accuracy or completely new functionalities. Quantum cryptography is one such technology: communication whose security is guaranteed by fundamental laws of quantum mechanics. The implementation of quantum cryptography exploits the ability to generate single photons of light on demand. Several different physical systems have been used to generate single photons, but very few of them are suitable for commercial production. An ideal single photon source should be fast, cheap and efficient, operate at room temperature, and emit photons at the wavelengths used in existing optical-fibre telecoms networks. A practical single photon source is expected to be somewhat like a type of semiconductor laser diode called a vertical cavity surface emitting laser (VCSEL). We will assess the feasibility of massproducing low-cost single-photon sources in the form of single-photon light emitting diodes (SPLEDs). These will exploit the unique properties of semiconductor nanostructures called self-assembled quantum rings, which we have recently used in novel VCSELs that operate at very low currents and at temperatures up to 110 degrees C.

Planned Impact

The exploitable results of this project are: (i) Single photon LED devices with GaSb/GaAs active material, (ii) Academic IP relating to fundamental properties of GaSb/GaAs optical properties and device design, and (iii) A UK supply chain from research to product feasibility in an important emerging technology.

After a successful outcome of this project, the consortium intends to continue development into a fully realised commercial product in the form of a packaged semiconductor chip single photon source. It is expected that this would be take the form of a TO-header-type package typical of laser and LED devices currently used in telecoms and datacoms applications. IQE is the world's leading supplier of III-V epitaxy with product lines that include light-emitting devices such as LEDs and vertical-cavity surface emitting lasers (VCSELs). CST Global Ltd has an existing supply chain for TO-header products, so the current project consortium embodies a full UK supply chain to manufacture and package the SPS chip. To pull the proposed device through to a genuine product fit for a quantum telecommunications application will require specialist expertise in commercial aspects of quantum technologies and its application to communication, which Quantum Base brings to the consortium. A large-scale system integrator is required to make the product viable for the end user and CIP Technologies (Hauwei) Ipswich have expressed interest in delivering this. After the end of this programme the consortium will require a further two year co-funded development project. It is expected that new partners fulfilling system integrator and end-user roles will join the current consortium. A further year of pre-production is envisaged before the commercial product would be launched. The consortium intends to disseminate scientific advances in high impact journals such Nature Photonics, Nature Communications and Applied Physics Letters, and will target talks at national and international conferences such as SIOE Cardiff, UK Semiconductors, MSS-2017. CST will actively market progress towards single photon source including at the Photonics West Trade Exhibition in California in February 2018.

Direct economic benefit to the industrial members of the consortium is expected from the marketing and sales of the resultant single photon source devices. Manufacturing of this product will be exclusively carried out in the UK until volumes are high enough to justify to subcontracting the assembly stages. The forecast revenue total is £4 million by 2023 split between industrial partners at a projected return on investment of ~300%. A successful commercialisation of the fundamental academic research at Lancaster University will have a positive impact on the research impact status (REF) allowing it to attract enhanced funding and improve student recruitment. The UK technology community as a whole will be supported by the generation of a quantum device supply chain.

Direct production of these high value quantum devices will result in safeguarding existing employment in the UK III-V component manufacturing industry, a vital enabling high technology capability vital to many UK companies, of which CST and IQE play a unique and critical part. Increased employment at CST would be needed to set up the product
manufacturing line.


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Description LEDs typically have a broad Gaussian emission, with a peak and intensity that drops away exponentially at longer and shorter wavelengths then the peak wavelength. We have found that by embedding self-assembled GaSb quantum rings in an optical cavity the intensity of long-wavelength tail of emission from the rings was enhanced ~800x at the resonant wavelength of the cavity, such that it exceeded the peak intensity by a factor of three. We attribute this effect to a drastic shortening of the naturally-long recombination time of the quantum rings by the resonant action of the cavity. This is a very desirable feature for the fabrication of single photon sources. Furthermore, the emission was at 1480 nm, close to the optimum wavelength for optical transmission using optical fibres, and was at room temperature.

We also found that demonstrating single photon emission at wavelengths beyond 1000 nm is experimentally very challenging, due to the reduced sensitivity of InGaAs detectors that operate at those wavelengths, compared to Si-based CCDs that work from the visible to 1000 nm.
Exploitation Route We plan to continue to work on this research, and have already submitted a bid for European funding. We will continue to look for opportunities to carry on the work, including with our established industrial partners.
Sectors Digital/Communication/Information Technologies (including Software),Electronics,Security and Diplomacy

Description A photon source is disclosed. The photon source comprises a semiconductor device comprising a first nanostructure and a second nanostructure, and control circuitry operable to apply an electric pulse to the semiconductor device so as to cause the first nanostructure to emit one single photon. The photon source is configured such that when the electric pulse is applied to the semiconductor device, only a single electron or only a single hole is provided to the first nanostructure via the second nanostructure. 
IP Reference WO2018162894 
Protection Patent application published
Year Protection Granted 2018
Licensed No
Impact The patent application has lapsed.