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.
Source:IOPscience
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