Surface studies of SiC epitaxial layers grown by chemical vapor deposition

We have systematically carried out investigations on the growth of SiC epitaxial layers by varying C/Si ratio over the range of 0.5, 1.0, 3.0, 6.0, and 9.0 in the gas phase. The studies by an optical Nomarski microscope and an atomic force microscope revealed the growth of hillocks and nano-tube like structures for particular deposition conditions on the C-face ( 0   0   0   1 ¯ ) and Si-face (0 0 0 1) 4H-SiC substrates. Indeed, at extreme conditions, the triangular shape hillocks formation was found on the C-face 4H-SiC substrates whereas on the Si-face 4H-SiC substrates, the cone or dome shape structures exhibited were black in color. Several carrot-like type structures, pits, etc., were also observed on the surface of the epilayers, which affect the quality of the layers and reduce the device efficiency. At optimized conditions, the surface looked like featureless with low roughness. In addition to C/Si ratios, N2 dopant into SiC epitaxial layers have also been studied.