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Growth, microstructure and morphology of epitaxial ScGaN films



Epitaxial ScGaN films were grown on GaN-on-sapphire substrates by NH3-molecular beam epitaxy (MBE). The Sc content remained below 2% for all films, as determined by the simulation and fitting of 0002 ω–2θ X-ray diffractograms, while no deviation from the wurtzite structure was detected using high resolution X-ray diffraction. ScGaN growth rates decreased significantly as the Sc flux increased and remained low compared to the growth rates of GaN grown under similar conditions, while Sc incorporation rates remained low even at Sc effusion cell temperatures as high as 1400 °C. Atomic force microscopy (AFM) height images indicate that higher Sc fluxes are associated with improved film coalescence. These data indicate that a surfactant layer of Sc may be present at the film surface during growth. The dislocation density of the lower Sc content films was similar to that of the underlying GaN, though the bending and introduction of additional dislocations with an a-component was observed for higher Sc contents. Basal plane stacking faults connected by prismatic stacking faults were also observed, in higher Sc-content ScGaN films, along with a broad luminescence band near 580 nm.