Characterisation of Epitaxial Lateral Overgrown GaN by Electron Backscatter Diffraction Correlated with Cross-Sectional Cathodoluminescence Spectroscopy F. Sweeney,* C. Trager-Cowan,* P. R. Edwards,* A. J. Wilkinson,** and I. M. Watson*** * SUPA, Department of Physics, University of Strathclyde, Glasgow G4 ONG, Scotland, UK ** Department of Materials, University of Oxford, Oxford OX1 3PH, UK *** SUPA, Institute of Photonics, University of Strathclyde, Glasgow G4 ONW, Scotland, UK Nitride semiconductor based light emitting diodes (LEDs) and laser diodes (LDs) are now being extensively used in consumer electronics because they are durable, energy efficient and available with bright light emission from the Ultra-Violet to the green region of the spectrum. These nitride- based optoelectronic devices are now being employed in traffic lights, backlights for displays, Blue- Ray DVD, surgeon’s goggles and curing lamps for dentistry (Fig. 1). However the most exciting development in the nitrides has been the advent of the white nitride based LED. These white LEDs are set to replace traditional incandescent and fluorescent lighting and are therefore going to revolutionise the way our homes and offices are illuminated in the next decade. Manufacturers of nitride based LEDs and LDs are seeking ways to increase device efficiency and longevity. To achieve this dislocation densities in nitride films have to be reduced; typically a Gallium Nitride (GaN) epilayer grown heteroepitaxially on a sapphire substrate can have a dislocation density as high as 10 10 cm -2 . A common growth method for reducing dislocation densities in GaN is Epitaxial Lateral Overgrowth (ELO). In the ELO growth process the final epilayer grows vertically and laterally simultaneously through and over a dielectric mask. This can results in a 10 3 reduction in the dislocation density in the ELO regions above the mask. In this presentation we shall report on our strain investigations of a just-coalesced 4μm thick ELO GaN epitaxial layer. In our study we used two independent techniques: Cathodoluminescence (CL) hyper-spectral imaging and Electron Backscatter Diffraction (EBSD). CL allows us to attain a wealth of information about the optical properties of a crystalline semiconductor with sub-micron resolution. The width and position of a peak in a luminescence spectrum is sensitive to strain, crystallinity, defects, doping and free carrier concentrations. EBSD is a technique for probing the structural properties with high spatial resolution (~50 nm). An EBSD pattern is a direct 2-D gnomonic projection of the crystal structure and is therefore suitable for the observation of changes in the crystal structure due to strains, tilts and rotations. The EBSD strain resolution achieved in this work is ± 2×10 -4 [1]. Fig 1: Applications of nitride semiconductors (a) World’s first ever blue-ray DVD recorder (b) LED Backlit Mobile Phone (c) White LED goggles for surgeons and (d) “The Weir” in the City of Glasgow floodlit with nitride LED’s, courtesy of Steve Hosey. (a) (c) (d) (b) Microsc Microanal 12(Supp 2), 2006 Copyright 2006 Microscopy Society of America DOI: 10.1017/S1431927606067705 1516 CD https://doi.org/10.1017/S1431927606067705 Published online by Cambridge University Press