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

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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.