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.
The project also involves development of new technologies in advanced nanofabrication, next generation wireless communication, III-nitrides and organic materials, which are all important frontiers of current scientific research. These all align extremely well to EPSRC priority areas, such as Manufacturing, Digital Economy, Energy and Healthcare as well as the priority themes and competences of the Technology Strategy Board (TSB). The vibrancy and importance of III-V activities in the UK are demonstrated by the report from the recent Road-mapping exercise in III-V semiconductors (2012). III-nitride LEDs were ranked as one of the highest priorities, with direct impact on 4 of the top 10 technologies. The proposed devices will also have significant impact on high data rate devices for telecoms, which came out top in the applications vs technology matrix. This research on III-nitrides will contribute to the development of a sustainable, energy-consumption-efficient world with very healthy and secure communication systems over the next 10-50 years.
Both applicants have strong track records in collaboration with the semiconductor optoelectronics industry. Seren Photonics Ltd, the industrial partner of the project, was established on Professor Wang's research innovations. Both have established extensive formal and informal collaborations with the semiconductor industry in the UK and overseas, including IQE (Cardiff), Enfis (Swansea), Forge Europa Ltd (Cumbria), Zeta-control (Oxford), and Plessey semiconductor (Swindon/Plymouth), Osram (Germany), OptoGaN (Russian), etc. Exploitation opportunities of any Sheffield-IP generated will be carried out by the University's Research and Innovation Services (RIS), and commercialisation will be assisted by Fusion IP, an AIM-listed public company which has signed a longer term agreement with the University on commercialising university research.
Professor Martin has worked closely with the semiconductor industry, and has a number of patents in III-nitride technologies. He has recently competed industrial projects with SemiMetrics Ltd. and McCann Energy Ltd.. In addition to the valuable input from Strathclyde's Research Office the Physics Department is host to the KT Directorate of the Scottish Universities Physics Alliance (SUPA-KT) which provides excellent help in identifying commercial partners and opportunities. He is a lead partner in the Intelligent Lighting Centre within Strathclyde's £100 M Technology and Innovation Centre (TIC), where new laboratories for this work will be completed in early 2014, bringing together high numbers of academic and industrial researchers across a wide range of disciplines. A number of TIC partners offer high potential for engagement with the work in this project, for example, the Fraunhofer Centre for Applied Photonics.
|Description||1. Develop a cost-effective epitaxial overgrowth method for semipolar GaN, leading to achieving high performance long-wavelength visible emitters with ultra fast response for both next generation solid state lighting and visible light communications
2. Develop a novel fabrication method to achieving hybrid organic/III-nitride emitters with ultra fast response and strong polarisation for next generation backlighting and solid state lighting
3. Understand the mechanism of defect reduction in overgrowing semipolar GaN on large lattice-mismatched substrates
4 Understand the mechanism of non-radiative energy transfer between inorganic and organic semiconductors
|Exploitation Route||The epitaxial growth method can be used in a wide range of areas, in particular, semiconductor industry and academy via a spin out company, and further large and disciplinary collaboration.
This findings have been highlighted by a number of semiconductor magazines and media world wide, such as
Digital/Communication/Information Technologies (including Software),Electronics,Energy,Environment,Healthcare,Manufacturing, including Industrial Biotechology,Transport
|Description||Part of the technologies will be planned to transfer to a spinout company, Seren Photonic Ltd. Seren has been awarded 2015 Royal Society Emerging Technology Award due to a major technological breakthrough in developing a cost effective method for semipolar GaN overgrowth. Part of the results have contributed to Seren Photonics Ltd's latest funds-raise and a few grant applications|
|First Year Of Impact||2014|
|Sector||Digital/Communication/Information Technologies (including Software),Electronics,Energy,Environment,Manufacturing, including Industrial Biotechology|