Microstructure and strain-free lattice parameters of ScxGa1-xN films

Moram, M A and Joyce, T B and Chalker, P R and Barber, Z H and Humphreys, C J and Kuball, M and Myers, T H and Redwing, J M and Mukai, T

Abstract.

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 800°C 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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Department of Materials
Imperial College London
Royal School of Mines
Exhibition Road
London, SW7 2AZ - UK