Setting LWIR state of the Art using T2SL detectors (LIRA)

The infrared regime has become the next frontier in the future of photonics providing crucial information from our environment which we cannot see with our eyes. There is a need for high-performance detectors, i.e. quantum (photonic) infrared detectors with high detectivity (low dark current and high quantum efficiency), for specific military (soldier vision enhancement, missile tracking/seeker) and space (earth observation) applications.

This PhD research project will focus on Type-II SuperLattice (T2SL) material as the device absorption region since it is considered a promising candidate for the next generation of high-performance infrared imaging systems (high operating temperature, multispectral, large focal plane array). Thanks to its unique properties, this material has theoretical potential to outperform, in the long-wavelength infrared (LWIR) spectral domain, state-of-the-art infrared technologies such as Mercury Cadmium Telluride (MCT) and GaAs/GaAlAs Quantum Well Infrared Photodetector. However, its theoretical performance has not yet been reached; this is directly related to the low minority carrier lifetime due to defects in the T2SL material. Our approach to achieve high-performance detectors is to explore the relationship between T2SL design, epitaxy and overall device design to achieve state-of-art performance in the 8-12micrometre spectral regime.

This project has great opportunity for scientific and industrial impact. We will explore the most important challenges in this wavelength regime and develop those promising approaches towards room-temperature operation of LWIR detectors and focal-plane arrays. We will identify defect types in the MBE-grown epilayers then mitigate their influence on device performance. We will explore sophisticated device design and architecture. Moreover, we will compare native GaSb substrates to industrially relevant GaAs and identify the optimum combination of substrate (material, type, orientation) and device design for industrial application, scale-up and potential focal plane array development.

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.