Thick and Smooth Hexagonal GaN Growth on GaAs (111) Substrates at 1000°C with Halide Vapor Phase Epitaxy

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Abstract
It was found that hexagonal GaN with a smooth surface can be grown on GaAs (111) substrates at temperatures as high as 1000°C by introducing a GaN layer grown at an intermediate temperature such as 850°C with halide vapor phase epitaxy (HVPE). The surface of the GaN layer grown at 850°C was rough but it became smooth surface when GaN was grown on it at 1000°C, though sometimes there were several hexagonal pits on the surface. There seems to be some surface flattening mechanism for hexagonal GaN growth at temperatures around or higher than 1000°C. The θ-2θ X-ray diffraction (XRD) of the grown layer showed only a hexagonal (0002) peak even for the layer grown at 850°C, but the full width at half maximum (FWHM) of the ω scan was improved by the growth of hexagonal GaN at 1000°C on it.