There is a significantly increasing demand for sustainable energy-efficient technologies due to the world energy crisis and climate change. The energy consumed due to general illumination accounts for about 29% of the world's total energy consumption, currently using rather inefficient technologies often containing toxic elements. It is therefore necessary to develop ultra energy-efficient solid-state lighting sources to replace these incandescent and fluorescent lights, for which the leading candidates are mainly based on white light emitting diodes (LEDs). Such white LEDs can be fabricated from inorganic or organic semiconductors, with the former leading the way for high brightness and efficiency. These are constructed from III-nitride semiconductors, which have direct bandgaps across their entire composition range, covering the complete visible spectrum and a major part of the ultraviolet. Fast modulation of the white LEDs, at speeds undetectable to the eye, allows them to also be utilised as optical transmitters for wireless data communication. This opens up the exciting possibility of white LEDs serving as lighting sources for simultaneous illumination and wireless communication. This is the emerging technology of visible light communication (VLC) and has a number of major advantages over the present-day radio frequency (RF) communication technology, such as increasing security, eliminating any RF-induced health concern, etc However, the performance and cost of current white LEDs is not sufficiently impressive to allow replacement of conventional lighting sources at the moment. Furthermore, in terms of VLC applications, the bandwidth is currently limited to the MHz level, which is well below the practical requirements of current broadband WiFi systems. This is due to the long carrier recombination lifetime of current III-nitride based LEDs, which are conventionally grown in a "polar" orientation containing intense piezoelectric fields. These fields result in a reduced overlap between the electron and hole wavefunctions in the active regions of the LEDs, which then suffer from long radiative recombination lifetimes (10-100 ns) and also low internal quantum efficiency. In addition, the conventional phosphors used to convert the emission to white light have even longer decay times and presents an additional limitation on the available bandwidth. The project will employ non-polar III-nitrides and integrate the two major semiconductor families (organic and inorganic semiconductors) using a novel nanofabrication technology in order to achieve ultra energy efficient LEDs with ultrafast modulation speeds for next generation III-nitride based white lighting. Structuring on a nanometre scale will be used in the growth of the III-nitride layers to achieve high quality non-polar GaN, thereby eliminating the piezoelectric fields to give faster, more efficient devices. The nanostructures will also be used to introduce extra nanocavity effects, further reducing the radiative recombination lifetime and increasing the optical efficiency. The target of the project is a novel hybrid nanostructure to achieve prototype white-LEDs with a modulation speed on a level of 10 GHz and a step change in energy efficiency compared with the current state-of-the-art. The devices will be fabricated using metal-organic vapour phase epitaxy and cleanroom processing and fully characterised using optical and electrical measurements. Each stage in the process will be optimised and close working with industry will ensure that the resulting methods are practical and scalable to high volumes.

N/A - see case for support

The goal of this proposal is to develop advanced fabrication processes for Gallium Nitride (GaN) and related materials (AlN and InN), collectively the III-Nitrides, for the 21st Century manufacturing industries. The III-Nitrides are functional materials that underpin the emerging global solid state lighting and power electronics industries. But their properties enable far wider applications: solar energy conversion by photovoltaic effect and water splitting, water purification, sensing by photonic and piezoelectric effects and in non-linear optics. Many applications of these functions of the III-Nitrides are enhanced, even enabled by creating three dimensional (3D) nanostructures. As such, the particular focus of the proposed research is to develop and nanostructuring processes on a manufacturing scale and to unlock the potential of these properties of the III-Nitride semiconductors in a range of innovative materials and devices. The research will address and resolve 1) the need of industry to be able to scale-up laboratory-based results based on individual piece or wafer fragments to batches of wafers of up to 6 inches in diameter, 2) the need to be able to design devices that are robust with the manufacturing tolerances, and 3) the need to rapidly characterise the devices to increase packaging yield. Potential commercial exploitation of the manufacturing processes and innovative materials and devices will be aided and led by the applicants' company partners. The programme of research opens with developing the core capability of wafer-scale (up to 6 inch) nanopatterning by nanoimprint lithography and the newly developed technique of Displacement Talbot Lithography, a potentially disruptive technology for generating nanostructures. These lithographic techniques will then be integrated with additive and subtractive processes to form 3D nanostructures across whole wafers. In a major application, the developed nanofabrication techniques will be used in developing manufacturing processes for the growth by metal organic vapour phase epitaxy (MOVPE) of non-polar and semi-polar GaN templates to address the persistent problem of the quantum confined Stark effect limiting the efficiency of light emitting diodes (LEDs) and GaN based laser diodes. The computer aided design method known as Designing Centering will be developed for process optimisation to maximise the yield of nanostructured devices (initially LEDs). Another activity will be to explore the use of electron beam and optical techniques, which are capable of characterising materials and devices on the deeply sub-micron scale, as production tools for screening materials and part-processed devices. The combination of wafer-scale nanofabrication techniques, advanced MOVPE growth, characterisation methods and Design Centering will then be deployed in the design and manufacture of innovative and emerging devices including core-shell structures for LEDs and photovoltaic applications, and nano-beam sensors that incorporate photonic crystals. Having established the core capability for the III-Nitrides, it will be extended to nanostructuring other semiconductors, notably InP and related materials as used in the manufacture of devices for optical fibre telecommunications.

We will establish the primary global manufacturing research hub for Compound Semiconductors that brings together Academic and Industrial researchers. This will capitalize on existing academic expertise in Cardiff, Manchester, Sheffield and UCL and the UK indigenous corporate strength in the key advanced materials technology of Compound Semiconductors. Cardiff, the Compound Semiconductor Centre and the other spoke universities will provide > £100M of additive capital leverage to the Hub, providing European leading facilities for large scale compound semiconductor epitaxial growth, device fabrication and characterisation enabling the most effective translation of research to manufacturing. The hub will operate at the necessary scale and with the necessary reach to change the approach of the UK compound semiconductor research community to one focused on starting from research solutions that can be manufactured. It will do this by providing the necessary tools and expertise and will become the missing exploitation link for the UK compound semiconductor research community. It will be a magnet and the driver for high technology industry and will act as the focal point for Europe's 5th Semiconductor Cluster and the 1st dedicated to compound semiconductors. Partners will include local and UK companies and global organisations. The importance of compound semiconductor technology cannot be overstated. It has underpinned the internet and enabled megatrends such as Smart Phones and Tablets, satellite communications / GPS, Direct Broadcast TV, energy efficient LED lighting, efficient solar power generation, high capacity communication networks, data storage, ground breaking healthcare and biotechnology. Silicon has supported the information society in the 20th century and dominates memory and processor function, but is reaching fundamental limits. Whilst the combination of Silicon and compound semiconductors will produce a second revolution in the information age, they are very different materials with, for example, different fundamental lattice constants and different thermal properties and have different device fabrication requirements. We propose research into large scale Compound Semiconductor manufacturing and in manufacturing integrated Compound Semiconductors on Silicon. The scale of the hub means we can bring together three world leading researchers in the growth of compound semiconductors on Silicon. Each has individually invented different solutions to tackle the silicon / compound semiconductor interface - together they will invent the universal solution. We will solve the scientific challenges in wafer size scale-up, process statistical control and integrated epitaxial growth and processing to facilitate new devices and integrated systems and open up completely new areas of research, only possible with reliable and reproducible fabrication, such as electronically controlled Qubits. We will facilitate the improved communication infrastructure necessary for the connected world and the integrated systems of the Internet of Things. We will produce large area integrated sensor arrays for, e.g. in-process Non-Destructive Testing, further benefiting manufacturing but also improving our safety and security. The key outcomes will be to 1) To radically boost the uptake and application of Compound Semiconductor technology by applying the manufacturing approaches of Silicon to Compound Semiconductors, 2) To exploit the highly advantageous electronic, magnetic, optical and power handling properties of Compound Semiconductors while utilising the cost and scaling advantage of silicon technology where best suited and 3) To generate novel integrated functionality such as sensing, data processing and communication.