Advanced III-nitride materials for next generation UV emitters used in water purification, environmental protection and local network communication

Lead Research Organisation: University of Sheffield
Department Name: Electronic and Electrical Engineering


The delivery of a sustainable future needs an excellent management of natural resources and also requires the world's environment to be maintained in good condition. Both of these are crucial for maintaining sustainable development and can be promoted by the development of advanced materials which can be fabricated into improved ultraviolet (UV) light sources. 280 nm or sub-280 nm UV light sources have many important applications in establishing high standard infrastructures, such as water purification, environmental protection, local network communication, medical equipment decontamination, etc.

Therefore, it is crucial to obtain advanced materials with these multiple functions in high crystal quality which can be fabricated into compact, light-weight and robust 280 nm UV emitters with high efficiency. The III-nitride semiconductor alloy AlGaN, has a direct bandgap across its entire composition range, covering a major part of the UV spectrum from 210 to 365 nm, and is the best material system to realize such a lighting source. The last decade has seen impressive developments in III-nitrides. However, the achievements are largely limited to the InGaN/GaN material system for the fabrication of the emitters mainly in the visible spectra region. High Al content AlGaN or AlN are required to achieve emission at 280 nm. In the last decade, considerable effort has been to the development of deep-UV III-nitride materials world wide. However, the results are far from satisfactory. The major issue is due to AlGaN or AlN material currently grown on c-plane substrates. These polar III-nitride semiconductor materials lead to a number of severe fundamental limits in science and technology, which are heavily restricting further development of deep UV emitters.

The proposed project will combine our extensive and complementary experiences in advanced metal-organic vapour phase epitaxy (MOVPE) growth and nanofabrication technology (Sheffield), optical and electron-beam studies of III-nitrides (Strathclyde), micro-structural investigation (Imperial), and advanced Hydride Vapour Phase Epitaxy (HVPE) growth for free-standing AlN substrate and flip-chip device fabrication (Nanjing, China). The combined research and development programme aims to achieve an understanding of the interrelated individual issues, and then to achieve advanced non/semi-polar AlGaN or AlN which will be applied to the demonstration of a new type of non/semi-polar LEDs. We also aim to develop the first 280 nm UV laser diode (non/semi-polar LDs), while the shortest wavelength laser diode reported so far is limited to 336 nm.

Planned Impact

The proposed work will lead to extensive impacts on technologies, society, economy and environment. More than 3.4 million people across the world die each year from water, sanitation, and hygiene-related reasons, and 780 million people lack access to an improved water source. In China, rapidly economic development is leading to generation of more and more industrial wastewater. This increases a high risk of contaminating the environment and also causes a significant reduction in water consumption per person. The severe air-pollution has led to a new policy for limiting the usage of private vehicles in the large cities in China. The air-pollution also exists in the large cities in the developed countries, such as UK, USA, etc., partially contributing to current climate change, which has been strongly evidenced by very recently severe flooding in the UK and extreme weather conditions in US.

The project will lead to major economic impact in both the UK and China. The Nanjing team has signed an agreement with the local government in order to promote technology commercialisation on III-nitrides. The Nanjing team and Sheffield team have established a joint research centre on III-nitrides. The international impact on both the UK and China will be further enhanced through the project using the joint centre as a platform.

Prof Wang's team and Seren Photonics Ltd as a spinout from his team have established extensive formal and informal collaborations with semiconductor industry in both the UK and overseas, such as IQE (Cardiff), Enfis (Swansea), Forge Europa Ltd (Cumbria), Zeta-control (Oxford), Plessey semiconductor (Swindon/Plymouth), Orsam (Germany), OptoGaN (Russian), Philip-Lumileds (USA) etc. Prof Martin has worked closely with the semiconductor industry, such as the semiconductor equipment company SemiMetrics Ltd. and lighting company McCann Energy Ltd.. He is a lead partner in the Intelligent Lighting Centre within Strathclyde's £100M Technology and Innovation Cente (TIC), 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.

Any technological breakthrough made through the project will impact a wide range of academic areas based on the study of III-nitrides through the UK Nitride Consortium (UKNC) and EPSRC National Centre for III-V Technologies which Sheffield is host to. The project will lead to widely academic impact in China through so-called "973" programmes on III-nitrides, where a large number of the research teams including Nanjing team in China are involved. The project will provide PDRAs and Ph.D students with an excellent opportunity to work in an interdisciplinary environment, offering excellent experience for their future career development. The training provided for the PDRAs and Ph.D students will have a direct economic impact via the provision of skilled workers which are critical requirements in maintaining the competitive edge of both UK and Chinese companies.

The project involves development of new technologies in advanced materials, nanotechnology, healthcare, wireless communication, all representing the frontiers in current research areas. All these also perfectly align to EPSRC priority areas, such as Manufacturing, Digital, Economy, Energy and Healthcare as well as with similar TSB areas. The vibrancy and importance of III-V activities in the UK were backed up by the recent Road-mapping exercise in III-V semiconductors (2012), where III-nitride LEDs has been ranked as one of the highest priorities. Its importance was further highlighted by its inclusion by David Willetts in his document 'Eight Great Technologies'. Research on III-nitrides, such as our proposed work, will contribute to the development of a sustainable world with high standard infrastructure over the next 10-50 years.
Description 1) Develop a new epitaxial growth approach for semipolar AlGaN for the applications in the ultraviolet (UV) spectral region, potentially next generation deep UV emitters
2) Understand the large lattice-mismatch induced cracking issue and then develop a simple method to meet the challenge
3) Understand the emission mechanisms of such a novel UV material
4) Demonstration of high crystal quality semi-polar AlGaN with high Al content on GaN regularly arrayed microrod templates, which is the best report
5) Optical investigation of semi-polar AlGaN with high Al content, for the first time demonstrating a reduction in exciton localization compared with its c-plane counterparts. This is very useful for the growth of deep UV laser structures
6) Micro-structural investigation to understand the defect reduction mechanism, showing a difference in reducing basal stacking fault density and dislocation density
7) Demonstrations of semi-polar AlGaN with an emission wavelength of around 260 nm, possibly the shortest wavelength for semi-polar AlGaN on sapphire so far
Exploitation Route It will be planned to transfer to the UK III-nitride semiconductor industry, and will contribute to a few joint grant applications to further benefit other Universities widely
Sectors Digital/Communication/Information Technologies (including Software),Electronics,Energy,Environment,Healthcare,Manufacturing, including Industrial Biotechology,Security and Diplomacy
Description 1) An ongoing discussion about a potential technology transfer with a start-up company 2) Part of developed technologies would be useful for a potential EU grant application and an EPSRC grant application under preparation 3) The technologies developed through the project have been highlighted at Industrial event organized by Professor Tao Wang, on 10 January 2017, Sheffield, attracting more than 10 semiconductor companies across the UK, where the CEOs or technical directors attended.
First Year Of Impact 2016
Sector Digital/Communication/Information Technologies (including Software),Electronics,Energy,Environment,Healthcare,Manufacturing, including Industrial Biotechology,Security and Diplomacy
Impact Types Cultural,Economic
Description A long term collaboration between Sheffield and Nanjing in the field of III-nitride Optoelectronics 
Organisation Nanjing University (NJU)
Country China, People's Republic of 
Sector Academic/University 
PI Contribution Nanjing University covers the major travel cost (domestic part) for the Sheffield team's visit to Nanjing, and the consumables costs for joint research activities at Nanjing
Collaborator Contribution The University of Sheffield covers the major travel cost (domestic part) for the Nanjing team's visit to Nanjing, and the consumables costs for joint research activities at Sheffield
Impact Professor Wang co-organised 1st Sheffield-Nanjing workshop held at Sheffield on 9-11 Feb 2015: 5 members from Nanjing University joined, 10 members from Sheffield, two external members from Strathclyde and Nottingham joined Professor Wang co-organised 2nd Sheffield-Nanjing workshop held at Nanjing on 13-17 December 2015 4 members from Sheffield, 12 members from Nanjing University As a Co-I, Professor Wang supported the Najing team's NSFC international programme grant application (led by Professor Lu, Hai) in both 2015 and 2016 As a co-organiser and one distinguished lecturer, Professor Wang delivered a lecturer at an international workshop on III-nitrides, held in Weihai, China, 27-30 August 2015 Professor Wang co-supervise a Ph.D student from Nanjing (Mr Zhuang, Zhe) Professor Wang and the Nanjing team is preparing a jointly grant application via the Innovate UK-China bridge programme in 2016: UK partners: University of Sheffield, Seren Photonics Ltd, Strathclyde China partners: Nanjing University; Nanjing Nanda optoelectronics Ltd
Start Year 2013