An efficient, practical and cost-effective means for directly converting heat into electricity is a very appealing concept. In principle, thermo-photovoltaic (TPV) cells could form the critical component of various systems for generating electricity from different types of heat sources including combustion processes, concentrated sunlight, waste process heat, and radio isotopes. This opens up a wide variety of possibilities for technology uptake and so TPV systems can be envisaged for use in applications ranging from small power supplies to replace batteries, to large scale co-generation of electricity. However, existing TPV cells are based on GaSb and are spectrally matched to heat sources at temperatures of ~1800 oC which limits their practical implementation and widespread uptake. GaInAsSb TPV cells with bandgap 0.53 eV have exhibited excellent performance with internal quantum efficiency near 95%. But, currently these are lattice-matched on GaSb substrates making them too expensive for practical implementation except in specialist high value or space applications. TPV development on larger format GaAs substrates will enable effective technology uptake through cheaper volume manufacturing of TPV cells. Consequently, there is a need to transfer the GaInAsSb cell architecture to GaAs. In this project we shall build on existing UK based world class III-V semiconductor materials expertise to fabricate novel low bandgap InGaAsSb TPV arrays on inexpensive GaAs substrates, capable of efficient electricity generation from thermal waste heat sources in the range 500-1500 oC commonly encountered in industrial processes. These monolithic arrays will be validated on-site together with our industry partners at Pilkington and MPIUK (Tata steel). The project will demonstrate the next step towards fabrication of large area TPV arrays essential for the commercial viability of TPV heat recovery, and will enable their widespread implementation in a wide range of high energy consumption industries such as glass, steel and cement manufacture, oil/gas and energy generation.

Compound Semiconductor (CS) materials are a Key Enabling Technology at the heart of modern society. They are central to the development of, for example, the 5G network, new energy efficient lighting, smart phones, satellite communications systems, power electronics for the next generation of electric vehicles and new imaging techniques. Simply put, these technologies support our connected world, our health, our security and the environment. The next generation of these technologies can only be achieved with a step change in CS manufacturing and we aim to the UK at the centre of this CS manufacturing research. This is not only important activity in its own right but will also support systems researchers in all of these important fields. The step change will be achieved by applying the manufacturing disciplines and approaches of Silicon to Compound Semiconductors and by combining CS with Silicon. This includes developing integrated epitaxial growth and processing with critical yield and reliability analysis; establishing new standards for CS device production, with a guaranteed number of wafer starts per week for key statistical based process control and development via IT infrastructure; solving the scientific and manufacturing challenges in wafer size scale-up combining large scale, 150-200mm diameter growth and fabrication for GaAs based and GaN based materials and apply this to existing and developed advanced processes; introducing a multi-project wafer culture (as is the norm in the silicon world) to share costs and encourage the widespread use of larger wafers by academics and SMEs. Critical to this approach is the characterisation equipment, which can be used in-line (during the manufacturing process) and over the larger (up to 200mm diameter) CS wafers we will utilise. This proposal is for this characterisation equipment to add to the large investment already made by Cardiff University and partners in epitaxial growth and fabrication infrastructure and equipment. We also ask for apparatus to allow high quality insulating layers to be deposited, which will enable the multi-project wafer approach to produce world leading performance, for access by our UK based circuit and system designers.

This proposal aims to bring to the UK an amazing microscope which will provide new and powerful capability in understanding the properties of light emitting materials and devices. These materials are key to many technologies, not only technologies that utilise the light emission from materials directly (such as energy efficient light bulbs based on light emitting diodes) but also a range of other devices which utilise the same family of materials such as solar cells and electronic devices for power conversion. Some of these technologies are in current use, but their efficiency and performance can be enhanced by achieving a better understanding of the relevant materials. Other target technologies are further from the market, but may represent the building blocks of our future security and prosperity. For example, the new microscope will provide information about light sources which emit one and only one fundamental particle of light (photon) on demand. Such "quantum light sources" are a potential building block for quantum computers and for quantum cryptography schemes which represent the ultimate in secure data transfer. How will the new microscope allow us to advance the development of all these technologies? It is based on a scanning electron microscope, which utilises an electron beam incident on a sample surface to achieve resolutions almost three orders of magnitude better than can be achieved using a standard light microscope. It thus accesses the nanometre scale, which is vital to addressing modern day electronic devices. Standard electron microscopy accesses the topography of a surface, but the incoming electron beam also excites some of the electrons within the material under examination into states with a higher energy. When these electrons relax back down to their usual low energy state, light may be given out, and the colour and intensity of that light is incredibly informative about the properties of the material under examination. This light emission can be mapped on a scale of ~10 nanometres so that nanoscale structures ranging from defects to deliberately engineered quantum objects can be addressed. This technique is known as cathodoluminescence, and has been in use for many years. The new capability of our proposed system is that it will map not only the colour and intensity of the light emission, but also allow us to measure the timescales on which an electron relaxes back down to its low energy state. We use the phrase "in the blink of an eye" to describe something that happens extraordinarily quickly. A real eye blink takes at least 100 milliseconds, whereas the relevant timescales for the electron to return to its low energy state could be almost 10 billion times quicker than this! The new microscope will be able to measure processes occurring on this time scale, by addressing how long after an electron pulse excites the material a photon is emitted. It will even be able to distinguish between photons with different wavelengths (or colours) being emitted on different time scales. Crucially, coupling this time-resolved capability with the ability to vary the temperature, we will be able to infer not only the time scales on which electrons relax to low energy sites emitting a photon, but also the time scales by which electrons reduce their energy by other, non-light-emitting routes. These non-light-emitting processes are what limit the efficiency of light emitting diodes, for example. Overall, across a broad range of materials, we will build up an understanding of how electrons interact with nanoscale structure to define a material's electrical and optical properties and hence what factors limit or improve the performance of devices. The proposed system will be the most advanced in the world, and will give UK researchers working on these hugely important photonic and electronic technologies a global advantage in developing new materials, devices and ultimately products.

The history of II-VI metal-organic chemical vapour deposition (MOCVD) goes back as far as IIII-V MOCVD but has not had the traction in applications for lasers, LEDs and high frequency devices that has been experienced by III-V semiconductors. A new generation of MOCVD equipment can more fully exploit the potential of II-VI semiconductors and explore new oxides and chalcogenides in the exiting areas of III-VIs such as Ga2O3 and 2-D semiconductors such as MoS2. There is now a compelling case for the UK to have state-of-the-art MOCVD equipment for compound semiconductors (CS) covering oxide and chalcogenide materials that are not covered by existing centres such as the National Epitaxy Facility at Sheffield, Cambridge and UCL, and Institute of CS at Cardiff. The UK has a golden opportunity to build on our strengths in CS research that will drive innovation across a range of new opto-electronic and power electronic devices. The need arises from a new generation of functional compound semiconductor materials to capture the unique properties of oxide and chalcogenide compound semiconductors (CSs), complementing III-V compounds and silicon, and opening new application areas in optoelectronics, energy and healthcare. It is proposed that we buy the Aixtron Close Couple Showerhead (CCS) reactor that has been proven to be the reactor design of choice for GaN deposition and will be the ideal equipment to deposit high quality oxide and chalcogenide compound semiconductor materials. "The UK needs this facility, which it does not have at present. Swansea is an excellent place for it." - Prof. Sir Colin Humphreys (Cambridge). "This proposed research facility will perfectly complement the installation of ~100 production MOCVD reactors leveraged by a £375M investment by IQE Plc over 2018-2022" - Dr Wyn Meredith (CSC, Cardiff). The CCS reactor will be installed in a new building for the Centre for Integrated Semiconductor Materials (CISM) (due for completion in Q1 2021) on the Swansea University Bay Campus. Over 140 m2 of specialist materials laboratory space will be allocated to the MOCVD reactor and complementary materials and characterisation equipment from Professor Irvine's laboratory. This new laboratory will be managed by Professor Irvine's team to provide high quality oxide and chalcogenide CSs to our research partners in Swansea University, other UK universities, industrial partners and to international collaborators. This will put the UK at the forefront of new science and technology using oxide and chalcogenide CSs for applications including high efficiency photovoltaic solar cells, Light harvesting quantum wire opto-electronic devices, piezoelectric energy harvesting, high breakdown voltage power electronic devices and light emitters. This new science and technology will benefit EPSRC priorities of "21st Century Products" and "Sustainable Industries" through enabling smart new products that could be rapidly prototyped through well proven manufacturing capability for MOCVD in the UK and enabling the application of more sustainable materials and reduced materials usage. This exciting opportunity is detailed in the case for support.

From an Information and Communication Technology (ICT) perspective, the 21st century is characterized by an explosion of requests for communication capabilities, high-performance computing, and cloud storage. Over the last few years, global Internet traffic has been growing exponentially. In this picture, transporting such an amount of data with existing electrical- interconnects and switching technologies will soon reach the "bottleneck" in terms of thermal loading, capacity, latency and power consumption. Optical- interconnects and switch fabrics combined with photonic integrated circuits (PICs) are seen as one of the most promising routes to push such limits. Silicon (Si) photonics is now considered as a reliable photonic integration platform. The beauty of Si Photonics stems from its ability to integrate microelectronics and photonics on a single Si chip utilizing standard CMOS IC technology. An important subset of this area is hetero-integration of III-Vs on Si, where the aim is the make use of III-V materials, with superior optical properties, to provide an efficient optical gain medium to circumvent the fundamental physical limitation of Si, i.e. Si cannot efficiently emit light, yet keeping the capability of light-routing, modulating, detecting and cost advantages of Si. In a breakthrough development, the investigators' group in UCL have shown that it is possible to grow epitaxially high-performance quantum dot (QD) lasers directly on Si substrates, opening up the possibility to monolithically integrate various types of III-V optoelectronic devices on Si. The pace of research on monolithic III-V/Si integration has then been dramatically accelerated and an increasing number of prestigious research groups including Bowers' group at UCSB and Arakawa's group at Tokyo University, and major Si chip companies, i.e. Intel, are currently devoting considerable programmes in this area. In addition to III-V/Si lasers, monolithic III-V/Si semiconductor optical amplifiers (SOAs) are also attracting significant interest as the key components for next-generation photonic integrated optical- interconnects and switching fabrics, as the application of SOAs is not limited only to compensate for loss and maintain signal levels as the signal propagates throughout a large number of optical components within the PICs, it is also used as a mature gating element for optical switches and has the advantages of ease of control, smaller footprint, low operating voltage, high ON/OFF extinction ratio, and fast transition times of the order of nanoseconds. However, such a III-V/Si SOA has not been developed to date. Building on the established expertise in monolithic III-V/Si QD lasers at UCL, this project proposal aims to develop the world's first monolithic III-V QD SOA on CMOS-compatible on-axis Si (001) substrates. In contrast to conventional native substrate based SOAs or III-V/Si SOAs using either flip-chip bonding or wafer bonding, the proposed method is fundamentally different, since the III-V SOAs will be integrated on Si by direct epitaxial methods, offering the possibility to achieve high-yield, low-cost and large-scale Si-based PICs, which is expected to be the technology platform to address next-generation optical- interconnect and switching solutions. With further development in Si photonics, i.e., providing the microelectronics world with the ultra-large-scale integration of photonic components, there will be scope to target applications in important areas such as consumer electronics, high-performance computing, medical and sensor solutions, and defence. This project will benefit from guidance from and joint work with both industrial as well as academic partners and will leverage major UK-based industrial and academic strengths in materials (e.g., CSC, EPSRC NEF) device processing (e.g., EPSRC CSHub, Glasgow) and photonics (e.g., Rockley, Lumentum), who are also well positioned to exploit this research.