Semiconductor materials power much of the current economy, through their use in the ubiquitous computer and much else besides. The most common semiconductor is silicon, and this accounts for about 90% of the world market. There are some other types of semiconductor, however, that provide functions that silicon can't address but which are also very important. Examples of these include: gallium arsenide, which is used in satellite receivers and mobile phones for the communications parts; materials based on indium phosphide, which are used in lasers in CD and DVD players and for long distance communications along optical fibres; and materials based on gallium nitride, which are used to make the white light emitting diodes that are now being used for a range of energy efficient lighting and even in car headlights. All of these materials belong to a family known as III-V semiconductors, because they contain a mixture of elements from group 3 and group 5 of the periodic table. III-V semiconductors account for most of the remaining 10% of the electronics industry, and are worth approximately £25bn per year worldwide and growing at about 7%p.a. Unlike the silicon industry, the UK has a significant presence in the manufacture of electronic components based on these materials, as well as systems based upon them, and is in a good position to benefit from the rapid growth in the market. Another member of this III-V semiconductor family in indium antimonide, a compound of indium and antimony, which has the formula InSb. InSb has several interesting properties. Charge carriers can be made to go faster than in any other member of the family and take less voltage to do so. Consequently, this material has the potential to make components that will operate at very high frequencies whilst consuming very little power and so, for example, enable future mobile devices to download massive amounts of data, such as streaming high definition video, without draining the battery or clogging the network. Another application is to enable imaging for detection of illicit explosives or firearms, without use of any harmful radiation. These materials might even find their way into future computers to enable the doubling of computing power to continue every two years, as it has for the last forty years. Other properties of the material mean that we can make infrared sensors for thermal imaging or detection of harmful gases, or photovoltaic devices that would make much more efficient solar energy systems. A corollary of these properties is that heat can cause the materials to "leak" charge, even at room temperature, so currently the only commercial applications are in high performance thermal imaging systems, where the application can tolerate the cost of having to provide cooling to -200C to make them work. This need to cool was previously assumed to be fundamental, however Ashley and co-workers have shown that this is not necessarily the case, and that uncooled operation is possible in several applications. This research will put in place the core technology that would enable a range of devices to be made that will work without any cooling. This technology includes being able to make features on the devices that are more than one thousand times smaller than a human hair and still have the devices operating effectively. It includes the addition of "nano-antennas" to the devices to improve their sensitivity to infrared light by orders of magnitude. It also includes work to show that the devices could be integrated with silicon, to benefit from the system cost savings derived from the massive investment in the silicon industry. The successful outcome of this research would be that various industries in the UK are able to quantify the benefits that the technology offers and make decisions to develop it into products. These would include the sensor manufacturers; prospective new companies in the mobile communications field; and renewable energy community.

There is great worldwide interest in the mid-infrared spectral region (2-5 um) as it contains the fundamental absorption bands of a number of pollutant and toxic gases and liquids. These include gases such as carbon dioxide, carbon monoxide and hydrogen chloride which require accurate, in-situ multi-component monitoring in a number of industries such as oil-rigs, coal mines, land-fill sites and car exhausts. Strong absorption bands also exist for drug intermediates, pharmaceuticals, narcotics and biochemicals where the absorption strength is typically 2 orders of magnitude stronger than in the near-infrared allowing highly selective and sensitive detection in the fields of: environmental monitoring, bio-medicine, industrial process control and health and safety. There is also an atmospheric transmission window between 3.6 and 3.8 um which enables free space optical communication and thermal imaging in both civil and military situations as well as the development of infrared countermeasures for homeland security. However, these applications have yet to be fully exploited due to the lack of efficient and affordable light sources and detectors. This work proposes the growth and fabrication of a new light emitting diode (LED) architecture based on indium antimonide (InSb) quantum dots onto low cost silicon (Si) substrates. This will revolutionize how we utilize these devices and lead to a dramatic scaling in the cost and size of the optical systems to enable their widespread uptake. It will also enable the photonic components to be directly embedded into electronic circuits which would open up a new field of mid-infrared photonic integrated circuits. This would generate entirely new technology in areas such as integrated 'lab-on-a-chip' sensors and compact biochips bringing great commercial benefits and opportunities to the UK. In the last few years, there has been significant progress in the development of mid-infrared devices using interband cascade lasers and type II superlattices. However these structures are extremely complex and expensive to fabricate and are grown on gallium antimonide (GaSb) substrates which are of poor quality, high cost (~50 times the cost of Si) and are only available in small sizes. Growth onto silicon would be most desireable to enable cost effective manufacture and to ensure future commercial success. The major obstacle in direct epitaxial growth of III-Vs onto Si is the large lattice mismatch between the III-V/Si interface, resulting in a large density of threading dislocations (TDs) which strongly deteriorate the device performance. This project shall overcome this by implementation of a new device design based on InSb quantum dots on low defect density GaSb buffer layers grown on Si. The key advantages are the mechanical robustness and very low sensitivity of the quantum dots to TD compared to bulk or quantum well structures, and the suppression of non-radiative Auger recombination to increase the quantum efficiency. In a quantum well device, every threading dislocation which propagates through it will act as a non-radiative centre drastically reducing the device performance. However in a QD, each TD will only 'kill' one or a few isolated dots which will not significantly affect device performance providing the TD density in the buffer layer can be reduced to moderate-to-low levels. Low defect density GaSb buffer layers shall be realized through novel 'interfacial misfit arrays (IMF)' and dislocation filtering layers designed to bend and annihilate TD generated at the III-V/Si interface. The Si based mid-infrared LEDs will be developed in close collaboration with academic (University of Southampton and University of Montpellier) and industrial (Compound Semiconductor Technologies and Gas Sensing Solutions) project partners to evaluate device performance for use in practical applications which will help to achieve future commercialisation.

Optical imaging is perhaps the single most important sensor modality in use today. Its use is widespread in consumer, medical, commercial and defence technologies. The most striking development of the last 20 years has been the emergence of digital imaging using complementary metal oxide semiconductor (CMOS) technology. Because CMOS is scalable, camera technology has benefited from Moore's law reduction in transistor size so that it is now possible to buy cameras with more than 10 MegaPixels for £50. The same benefits are beginning to emerge in other imaging markets - most notably in infrared imaging where 64x64 pixel thermal cameras can be bought for under £1000. Far infrared (FIR), or terahertz, imaging is now emerging as a vital modality with application to biomedical and security imaging, but early imaging arrays are still only few pixel research ideas and prototypes that we are currently investigating. There has been no attempt to integrate the three different wavelength sensors coaxially on to the same chip. Sensor fusion is already widespread whereby image data from traditional visible and mid infrared (MIR) sensors is overlaid to provide a more revealing and data rich visualisation. Image fusion permits discrepancies to be identified and comparative processing to be performed. Our aim is to create a "superspectral" imaging chip. By superspectral we mean detection in widely different bands, as opposed to the discrimination of many wavelengths inside a band - e.g. red, green and blue in the visible band. We will use "More than Moore" microelectronic technology as a platform. By doing so, we will leverage widely available low-cost CMOS to build new and economically significant technologies that can be developed and exploited in the UK. There are considerable challenges to be overcome to make such technology possible. We will hybridise two semiconductor systems to integrate efficient photodiode sensors for visible and MIR detection. We will integrate bolometric sensing for FIR imaging. We will use design and packaging technologies for thermal isolation and to optimise the performance of each sensor type. We will use hybridised metamaterial and surface plasmon resonance technologies to optimise wavelength discrimination allowing vertical stacking of physically large (i.e. FIR) sensors with visible and MIR sensors. We ultimate want to demonstrate the world's first ever super-spectral camera.

Photonics is one of the largest and fasted growing markets of the world economy. Optical technologies are key to a vast range of applications from telecommunications networks to sensor and metrology equipment and are being actively developed by industrial giants such as IBM, Intel and Cisco. In a similar way to the evolution experienced by electronics, the demand for photonics devices with smaller footprint, lower cost and higher functionality has propelled the rapid development of integrated "photonics chips". Thanks to the legacy provided by decades of enormous investments in the electronic industry, silicon is rapidly becoming the standard material platform for photonic integrated chips. However, because of its crystalline structure, silicon is a very poor light emitter and, therefore, truly integrated devices that can emit, process and detect light on-chip still represent a major challenge. III-V semiconductor materials such as InP or GaAs provide far better performance in terms of light emission but cannot compete with silicon in terms of large volume manufacturing and cost. Combining the "best from the two worlds", i.e. heterogeneously integrating III-V light emitters on a silicon material platform, is regarded as a promising solution to circumvent the deficiencies of silicon yet keeping compatibility with industrial silicon manufacturing paradigms to allow scaling to wafer level complex products without requiring a full retooling of the supply chain. Building on established expertise in photonic integrated devices and transfer printing technologies at Glasgow and Strathclyde universities, this proposal will develop an assembly technique to integrate active III-V membrane devices onto passive silicon photonic integrated circuits. The method will demonstrate parallel transfer of multiple devices with sub-micrometer positional accuracy and scalability to wafer-level production. The developed techniques will exploit fully back-end processes, making them compatible with current foundry standards and therefore commercial interests. Key demonstrators in optical communications, gas sensing and high density data storage will be developed to illustrate the flexibility of the methods and potential across a wide range of application spaces. The project will benefit from the support from several academic and industrial partners who will provide resources and expertise in key areas such as wafer-scale manufacturing of III-V optical devices (CST), transfer printing system engineering (Fraunhofer), optical transceivers for telecomm and datacentre markets (Huawei), micro-assembly of active/passive photonic systems (Kaiam), integrated photonic devices for HDD data storage (Seagate), mid-IR gas sensors (GSS), large-scale silicon photonics devices (Southampton University). The proposal aligns with EPSRC's Manufacturing the Future theme and the Photonics for Future Systems priority, and addresses specific portfolio areas such as Manufacturing Technologies, Optical Communications, Optical Devices & Subsystems, Optoelectronic Devices & Circuits, Components & Systems

Silicon Photonics, the technology of electronic-photonic circuits on silicon chips, is transforming communications technology, particularly data centre communications, and bringing photonics to mass markets, utilising technology in the wavelength range 1.2 micrometres - 1.6 micrometres. Our vision is to extend the technical capability of Silicon Photonics to Mid -Infrared (MIR) wavelengths (3-15 micrometres), to bring the benefits of low cost manufacturing, technology miniaturisation and integration to a plethora of new applications, transforming the daily lives of mass populations. To do this we propose to develop low-cost, high performance, silicon photonics chip-scale sensors operating in the MIR wavelength region. This will change the way that healthcare, and environmental monitoring are managed. The main appeal of the MIR is that it contains strong absorption fingerprints for multiple molecules and substances that enable sensitive and specific detection (e.g. CO2, CH4, H2S, alcohols, proteins, lipids, explosives etc.) and therefore MIR sensors can address challenges in healthcare (e.g. cancer, poisoning, infections), and environmental monitoring (trace gas analysis, climate induced changes, water pollution), as well as other applications such as industrial process control (emission of greenhouse gases), security (detection of explosives and drugs at airports and train stations), or food quality (oils, fruit storage), to name but a few. However, MIR devices are currently realised in bulk optics and integrated MIR photonics is in its infancy, and many MIR components and circuits have either not yet been developed or their performance is inferior to their visible/near-IR counterparts. Research leaders from the Universities of Southampton, Sheffield and York, the University Hospital Southampton and the National Oceanography Centre will utilise their world leading expertise in photonics, electronics, sensing and packaging to unleash the full potential of integrated MIR photonics. We will realise low cost, mass manufacturable devices and circuits for biomedical and environmental sensing, and subsequently improve performance by on-chip integration with sources, detectors, microfluidic channels, and readout circuits and build demonstrators to highlight the versatility of the technology in important application areas. We will initially focus on the following applications, which have been chosen by consulting end users of the technology (the NHS and our industrial partners): 1) Therapeutic drug monitoring (e.g. vancomycin, rifampicin and phenytoin); 2) Liquid biopsy (rapid cancer diagnostics from blood samples); 3) Ocean monitoring (CO2, CH4, N2O detection).