Epitaxial ScxGa1-xN films of low Sc concentration (x = 0.08 ± 0.01) were deposited on MOCVD-grown GaN films (using an Al2O3 substrate) at 800oC using molecular beam epitaxy employing ammonia as a reactive nitrogen source (NH3-MBE). The strain-free lattice parameters of the films were determined using a method based on high-resolution X-ray diffraction (HRXRD) in conjunction with an in-situ elastic tester. It is found that the c:a lattice parameter ratio increases slightly and that the Poisson's ratio decreases with increasing Sc concentration. The crystalline quality and long-range ordering of the ScxGa1-xN films (as indicated by HRXRD peak intensities and full width at half maximum values) is improved considerably relative to the GaN template. Our results indicate that threading dislocations do not propagate effectively into the ScxGa1-xN films and that these may therefore potentially find application as dislocation blocking layers in GaN-based optoelectronic devices.
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M. A. Moram would like to acknowledge support from the Engineering and Physical Sciences Research Council, the British Association for Crystal Growth and Corpus Christi College, Cambridge. The authors would also like to thank Dr. Menno Kappers and Dr. Rachel Oliver for growing the GaN templates and Mary Vickers for helpful advice on data collection using the high-resolution X-ray diffractometer.
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Moram, M.A., Joyce, T.B., Chalker, P.R. et al. Microstructure and Strain-Free Lattice Parameters of SCxGa1-xN Films. MRS Online Proceedings Library 892, 2807 (2005). https://doi.org/10.1557/PROC-0892-FF28-07