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Details of Grant 

EPSRC Reference: TS/G001448/1
Title: Green Laser Diodes
Principal Investigator: Kent, Professor A
Other Investigators:
Staddon, Mr C Foxon, Professor CT Campion, Dr RP
Novikov, Professor S
Researcher Co-Investigators:
Project Partners:
Department: Sch of Physics & Astronomy
Organisation: University of Nottingham
Scheme: Technology Programme
Starts: 01 April 2009 Ends: 31 March 2011 Value (£): 279,864
EPSRC Research Topic Classifications:
Materials Characterisation Materials Synthesis & Growth
EPSRC Industrial Sector Classifications:
Electronics
Related Grants:
Panel History:  
Summary on Grant Application Form
In this project, next generation semiconductor laser diodes emitting in the green wavelength range will be demonstrated. The lasers will be the first to be made from nitride semiconductors in the novel cubic phase by using cubic nitride semiconductor free-standing substrates that are unique to this project. These lasers will be the world's first long-lifetime monolithic green lasers, and will provide an enabling technology for a number of industries such as solid state lighting and image projection. The primary application of such lasers is the green component of Red-Green-Blue laser light modules for use in mini-projectors or as a white light source in general lighting and display backlights.The role of the Nottingham team will be to fully develop the unique substrates, and to supply them in sufficient quantity to Sharp Laboratories where the laser structures will be fabricated. These substrates are cubic phase (zincblende structure) gallium nitride (GaN). This type of substrate is known as non-polar and are essential to the project in order to eliminate the internal electric fields which have prevented the realisation of green nitride lasers up to now on conventional polar substrates.The Nitrides Research Group at the University of Nottingham has already made considerable progress on the development of free-standing cubic GaN substrates, and has filed international patents on the novel molecular beam epitaxy growth process used to produce them. Current development work is being carried out by the Nottingham group in collaboration with Sharp Laboratories as part of the Technology programme funded SULFIA project on UV lasers, which ends in March 2009. This collaboration has been highly beneficial to the substrate development work by providing direct feedback on the suitability of the substrates for growth of device structures. At this stage, it is clear that, while the substrates produced are highly suitable for growth research, they are not yet of commercial quality. To address this issue, in the proposed project the Nottingham team will focus on defect reduction in the bulk crystal and reducing the surface roughness to produce commercial quality epi-ready substrates.A range of characterisation techniques including X-ray crystallography, electron microscopy and photoluminescence spectroscopy will be used to assess the density of defects, e.g. hexagonal GaN inclusions, and impurities in the substrates. Using this information, the growth conditions, e.g. temperature and beam fluxes of gallium and nitrogen, will be optimised to reduce the defect density.Lapping and polishing processes will be developed to remove the defective surface layers and reveal the high quality material below, and to produce a new surface with roughness less than or equal to current commercially available (hexagonal) GaN substrates. The surfaces will be characterised by atomic-force microscopy and also optically.As well as improving the quality of the substrates, the Nottingham group will also investigate growth on larger, three-inch, wafers in order to improve the yield of 10x10 mm GaN substrates for use in the growth studies at Sharp Laboratories, and as the first step in scaling up the substrate growth process to industrial production standards.For many device applications it is useful to have doped (n or p-type) substrates. the Nottingham group will investigate doping of the substrates with various elements including magnesium and carbon. Hall effect measurements will be used to determine the free carrier density and polarity.
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Organisation Website: http://www.nottingham.ac.uk