Manufacturing of nano-engineered III-nitride semiconductors

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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.