Boosting Efficiency in Mm-Wave III-V Power Amplifiers

Several mass market applications are emerging in mm-wave bands, including 5G, satcom and mobile infrastructure (backhaul). The need for efficient power amplifiers is even more felt at these frequencies given an increased complexity of the transmitters (active arrays); this is in contrast with the intrinsic difficulty of designing at mm-wave frequencies. Moreover, efficient power amplifier design must rely on accurate waveform engineering whose feasibility at mm-wave frequencies is still unexplored.

III-V technologies have the potential of offering a boost in terms of performance compared to Si-based amplifiers. However, at mm-wave frequencies, a better understanding of non-linear operation in terms of waveforms is key in enabling more sophisticated design techniques as well as feeding-back to the transistor design o optimise operation.

The Centre for High Frequency Engineering at Cardiff University has recently acquired a £1.4m harmonic load-pull characterisation system with 110 GHz bandwidth and waveform measurement capability. The idea is to exploit the system to characterise, compare and model mm-wave transistors samples provided by Qorvo (GaAs and GaN). This will enable to explore and define the best power amplifier design technique to achieve high efficiency, as well as understanding how the devices can be improved to improve the performance. The technique developed will be tested on MMIC designs on GaAs and GaN.

Through our students, following consideration of the consequences of their research and appropriate action informed by their Responsible Innovation training, impact will fall into one of 3 strands:

SOCIETAL:

As a Key Enabling Technology, Compound Semiconductors (CS) bring benefit to society in general through developing the connected society, e.g. the 5G network, the smart phones that use it, satellite communications systems and data server infrastructure;

they contribute to reducing our carbon footprint through e.g. photovoltaics, new energy efficient lighting, and, power electronics for the next generation of electric vehicles.

CS sensor technology is at the heart of early medical diagnosis and CS based light sources are essential for both cosmetic treatments, such as hair removal, and life-saving treatments such as Photodynamic Therapy.

CS based magnetic sensors are being developed for security screening and next generation secure communication.

In total these technologies support our connected world, our health, our security and the environment.

ECONOMIC: The global market for CS is large, currently worth around $33.7Bn, with a compound annual growth rate of 17.3%.

The vision of the CS cluster was first defined in 2015, to build on existing academic and industrial assets, capability and manufacturing excellence to create Europe's 5th Semiconductor Cluster and the first in the world dedicated to Compound Semiconductor Technologies. To date the cluster has secured commitments of >£500M private and public investment with a suite of innovation assets and critical manufacturing infrastructure and a purpose to drive UK growth in the CS sector.

It is absolutely critical to recognise that the formation of clusters need ongoing nurturing, cross fertilisation of people and ideas and most importantly the supply of skilled staff to support rapid growth in order to reach critical mass for sustainability. The predicted PhD level jobs increase in just the current local cluster companies would more than use all of the minimum underwritten CDT output over the next 5 years, and we need to do much more. Our CDT is essential to support the development of key elements of the rapidly emerging Compound Semiconductor Cluster and drive new linkages within the wider UK industrial supply chain. Thus addressing the issue of bringing manufacturing supply chains back to the UK - a key element of the Government's Industrial Strategy.

The EPSRC CS roadmap document , June 2012, identified a concern that the UK CS Research Community is missing an exploitation link that can provide a route to impact and economic leverage EPSRC's >£20M pa CS research investment. Many technological solutions work well in the research laboratory or as one-off demonstrators but fail to translate to industrial production or commercial success. The CDT will directly address this issue by changing the mind-set of the next generation of researchers so that they start from solutions that allow rapid translation to production.

OUTREACH:

It is critical that the public and our politicians understand the excellence and importance of CS manufacturing in the UK. Our CDT cohort will undergo training in elevator pitches and media interactions to influence decision makers and will develop videos explaining how Compound Semiconductors are made and what they can do. They will inform a diverse set of people using a range of innovative formats such as performance and theatre production skills.

A crucial part of the people pipeline, which will support our future manufacturing excellence, is the motivation of our young people. Our CDT cohort will develop a Schools programme and an Undergraduate programme.

This will ensure we attract the very best and widest range of applicants and, most importantly, inform and excite the next generation about the opportunities that CS technology and Manufacturing offers them.