Surface Morphological Structures of 4H-, 6H- and 15R-SiC (0001) Epitaxial Layers Grown by Chemical Vapor Deposition

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Abstract
Surface structures of SiC epitaxial layers grown on 4H-, 6H- and 15R-SiC (0001) substrates have been investigated using an optical microscope and an atomic force microscope (AFM). SiC epitaxial layers of 5–15 µm thickness have been grown by chemical vapor deposition on 4H-, 6H- and 15R-SiC (0001) Si-face substrates with 0.2–8.0° off-angle. AFM observation reveals that macrostep formation with a submicron periodicity is reduced by increasing the off-angle of substrates, leading to a small surface roughness of 0.18–0.22 nm. The bunched steps with two and three Si–C bilayer heights are dominant for 4H- and 6H-SiC epitaxial layers, respectively, while 15R-SiC epitaxial layers show both two and three Si–C bilayer height steps, reflecting the peculiar stacking structure of each polytype. By optimization of the growth process, the surface defect density has been reduced from 1200–4500 cm-2 to 50–250 cm-2.