The sensing, processing and transport of information is at the heart of modern life, as can be seen from the ubiquity of smart-phone usage on any street. From our interactions with the people who design, build and use the systems that make this possible, we have created a programme to make possible the first data interconnects, switches and sensors that use lasers monolithically integrated on silicon, offering the potential to transform Information and Communication Technology (ICT) by changing fundamentally the way in which data is sensed, transferred between and processed on silicon chips. The work builds on our demonstration of the first successful telecommunications wavelength lasers directly integrated on silicon substrates. The QUDOS Programme will enable the monolithic integration of all required optical functions on silicon and will have a similar transformative effect on ICT to that which the creation of silicon integrated electronic circuits had on electronics. This will come about through removing the need to assemble individual components, enabling vastly increased scale and functionality at greatly reduced cost.

The properties of light are already exploited in communications, the Internet of Things, big data, manufacturing, biomedical applications, sensing and imaging, and are behind many of the inventions that we take for granted today. Nevertheless, there is still a plethora of emerging applications with the potential to effect positive transformations to our future societies and economies. UK researchers develop cutting-edge technologies that will make these applications a reality. The characteristics of these technologies already surpass the operating wavelength range and electronic bandwidth of our existing measurement equipment (as well as other facilities in the UK), which currently forms a stumbling block to demonstrating capability, and eventually generating impact. Several important developments, relating for example, to integrated photonic technologies capable of operating at extremely high speeds or the invention of new types of optical fibres and amplifiers that are capable of breaking the traditional constraints of conventional silica glass technology, necessitate the use of ever more sophisticated equipment to evaluate the full extent of their capabilities. This project aims at establishing an open experimental facility for the UK research community that will enable its users to experiment over a wide range of wavelengths, and generate, detect and analyse signals at unprecedented speeds. The new facility will enable the characterisation of signals in time and will offer a detailed analysis of their frequency components. Coherent detection will be possible, thereby offering information on both the amplitude and phase characteristics of the signals. This unique capability will enable its users to devise and execute a range of novel experiments. For example, it will be possible to experiment using signals, such as those that will be adopted in the communication networks of the future. It will make it possible to reveal the characteristics of novel devices and components to an extent that has previously not been possible. It will also be possible to analyse the response of experimental systems in unprecedented detail. The facility will benefit from being situated at the University of Southampton, which has established strong experimental capabilities in areas, such as photonics, communications and the life sciences. Research at the extended cleanroom complex of Southampton's Zepler Institute, a unique facility in UK academia, will benefit from the availability of this facility, which will enable fabrication and advanced applications research to be intimately connected. Furthermore, this new facility will be attached to EPSRC's National Dark Fibre Facility - this is the UK National Research Facility for fibre network research, offering access and control over the optical layer of a dedicated communications network for research-only purposes. The two together will create an experimental environment for communications research that is unique internationally.

TOPIC: "Semiconductors" are often synonymous with "Silicon Chips". After all Silicon supported computing technologies in the 20th century. But Silicon is reaching fundamental limits and already many of the technologies we now take for granted are only possible because of Compound Semiconductors (CS). These technologies include The Internet, Smart Phones, GPS and Energy efficient LED lighting! CSs are also at the heart of most of the new technologies expected in the next few years including 5G wireless, ultra-high speed optical fibre connectivity, LIDAR for autonomous vehicles, high voltage switching for electric vehicles, the IoT and high capacity data storage. To date CSs are made in relatively small quantities using fairly bespoke manufacturing and manufacturers have had to put together functions by assembling discrete devices. But this is expensive and for many of the new applications integration is needed along the lines of the Silicon Integrated Chip. CDT research will involve: the science of large scale CS manufacturing (e.g. materials combinations to minimise wafer bow, new fabrication processes for non-flat surfaces); manufacturing integrated CS on Silicon and in applying the manufacturing approaches of Silicon to CS. The latter includes using generic processes and generic building blocks and applying statistical process control. By applying these approaches students will address and invent new ways to exploit the highly advantageous electronic, magnetic, optical and power handling properties of CSs and generate novel integrated functionality for sensing, data processing and communication. NEED: This CDT is a critical part of the strategic development of a CS Cluster supporting activity throughout the UK. It is part of the development of a wider training portfolio including apprenticeships and CPD activities, to train and upskill the CS workforce. Evidence of the critical need for a CDT, has been identified in a survey and analysis conducted by UK Electronics Skills Foundation highlighting the specific skills required in this rapidly growing high technology industrial sector. "We are looking for PhD level skills plus industry experience. We don't have the time to train up new staff." "There are no 'perfect employees' for CS companies, as this is effectively a new area. Staff, including those with PhDs, either have silicon skills and need CS-specific training, or have CS skills and need training in volume tools and processes, either in the cleanroom or in packaging." - quotes from CS Skills Survey - Report UKESF July 2018. We have worked with the CSA Catapult utilising the skills need they have identified as well as companies across the spectrum of CS activities and are confident of the absorptive capacity: the expected PhD level jobs increase for the existing cluster companies alone would employ all the students and the CDT will support many more companies and academic institutions. APPROACH: a 1+3 programme where Year 1 is based in Cardiff, with provision via taught lectures using university approved level 7 modules and transferable skills training, hands on and in-depth practical training and workshop material supplied by University and Industry Partner staff. A dedicated nursery clean room to allow rapid practical progress, learning from peer group activity and then an industry facing environment with co-location with industry staff and manufacturing scale equipment, where they will learn the future CS manufacturing skills. This will maximise cross fertilisation of ideas, techniques and approach and maximise the potential for exploitation. Y2-Y4 consist of an in depth PhD project, co-created with industry and hosted at one of the 4 universities, and specialised whole cohort training and events, including communication, responsible innovation, entrepreneurship, co-innovation techniques and innovative outreach.

Ubiquitous, high-performance communication is the backbone of our society, and promises to play an increasing role not only in individual's daily lives, but just as importantly in the background with communication among devices (e.g. vehicle-to-infrastructure for mobility, process control and monitoring in industrial and manufacturing, virtualization of full environments for the metaverse, among others). The resulting explosion in data that must be processed and communicated requires extraordinary bandwidth and network ubiquity, which in turn demands supporting electronics that is high performance, power efficient, and low cost. This EPSRC - NSF proposal targets a great leap forward in the most critical link, the wireless power amplifier, that is essential to realizing a vision of ubiquitous, high-speed, transparent mobile communication. Power amplifiers are among the most critical elements in any communication system as they dictates the overall efficiency of the system. GaN-based HEMTs are especially promising for high-performance power amplifiers, but current GaN-based systems suffer from limited frequency coverage, efficiency and linearity due to a combination of factors, including device design e.g. use of field plates effectively limits operation to 30 GHz and below, and materials issues e.g. deep level traps, self-heating means that gain and efficiency degrade rapidly both with output power as well as frequency. We leverage in this programme transformative advances in both GaN-based transistor design and novel circuit topologies to dramatically improve the efficiency, bandwidth, linearity, and cost of the key wireless elements of a communication system, through co-design. The technology is based on polarization-engineeered graded channel GaN HEMTs that show a substantial improvement in linearity in comparison to conventional HEMTs. By combining with thorough investigation of their underlying device physics including trap states and thermal management, we address major effects that degrade the performance of GaN at increasing frequencies (i.e. Ka band up to 40 GHz) by optimizing device design and fabrication. We will design harmonically terminated amplifiers based on our new class of contiguous modes, that allow designers wider choice of impedances for desired characteristics of efficiency, linearity and output power. The project brings together world leading experts in the Universities of Notre Dame, Bristol and Sheffield, working alongside supporting industry in UK and US, that completes the entire supply chain from substrate growers, device/chip fabrication to circuit designer in both countries. The targeted enabling millimetre-wave communication technology is expected to be the next frontier in emerging applications that play a critical role in the levelling up agenda to drive prosperity in all regions of the UK, the US and worldwide. For example 5G is expected to underpin new industries worth $13.2T in goods and services in the UK alone by 2035.

Wireless communication systems require the translation of an information-bearing signal at higher frequencies (such as radio- or mm-wave frequencies) to allow propagation through the wireless medium (the channel). This translation is typically performed in transmitters and receivers that along with the channel form the communication system. In the transmitter, a power amplifier (PA) is used to boost the power of the signal to a level sufficient to overcome the channel's attenuation and arrive with sufficient signal strength at the receiver. Today's best PAs are capable of 60-70% efficiency when used at their maximum output power. This means that about 1/3 of the power is wasted into heat only for the purpose of amplifying at such higher frequencies. Efficiency decreases when reduced output powers are required. Modern communications standards such as 5G generate signals which present a large power variation over time (this is also described by the peak-to-average power ratio or PAPR) and this causes the PA to operate even more inefficiently with values down to 10-20%, instead of the aforementioned 60-70%. Wasting almost 90% of the DC power into heat causes additional demands on the energy supply network which may lead to an increase in carbon emissions. Higher DC power dissipations result in reduced transmitter performance (e.g. less output power and so less coverage), reduced battery lifetime, in additional weight, cost, and size because of the heatsinks and necessary cooling hardware. Heat dissipation causes the electronics within the PA to operate at higher temperatures which are known to degrade the component's reliability (ageing) and change their electrical behaviour. The goal of this project is to radically improve the RF PA efficiency by using a technique called supply modulation (SM). Unlike the 1952's envelope-tracking (ET) method, SM uses a very high-efficiency modulator to generate a number of voltage levels (Vmin, ..., Vmax) that are applied to the drain of the PA. When the RF output power in the PA is high, the PA is supplied with the maximum voltage level and so it operates at maximum efficiency. Vice-versa, when the PA output power is low, a lower voltage level is supplied to the PA drain. This change in the supply results in an efficiency improvement usually in the range of 20-30% (and so in a SM-PA efficiency of 30-50%), but most importantly, it typically reduces the DC power consumption by ~50% for the same output power. Achieving wider and wider bandwidths for high link capacities requires this SM-PA to commutate very rapidly as a consequence of a wideband signal. The current state-of-art bandwidth is ~100MHz for the SM-PA. Achieving 1GHz bandwidth, as required in multi-band and mm-wave PAs, is thus the target of this project. To achieve this, new circuit topologies combined with high figure-of-merit semiconductor technologies will be explored, with the unavoidable hardware imperfections compensated through signal processing techniques such as digital pre-distortion (DPD). The SMPA specifications and top-level design parameters will be agreed between the University of Bristol (UoB)'s team and the project's partners to ensure relevance for industrial applications. This SM-PA is firstly simulated in the SM part, then in the PA, and then co-simulated together as a complete sub-system. The fabricated prototype is then characterized in terms of linearity, efficiency, and power with the latest communication standards. The SM circuit can also be combined with existing PAs as an 'efficiency upgrade'. Results of this theoretical and experimental activity are presented at conferences and published in journals by the UoB team. Public engagement and industry impact is also ensured by the presence of an advisory board. In summary, this project is an adventurous research programme that will re-define next-generation RF transmitters amplifiers and so contribute to UK's leadership in wireless technologies.