Topographic and Reflectometric Investigation of Crystallographic Defects and Surface Roughness in 4H Silicon Carbide Homoepitaxial Layers Deposited at Various Growth Rates

Undoped 4H silicon carbide epitaxial layers were deposited by means of CVD method with growth rates of 2 mu m/h, 5 mu m/h and 11 mu m/h at 1540 degrees C on n-doped 8 degrees, 4 degrees and 0 degrees off-cut 4H-SiC (00 . 1) substrates. The structural defects were studied before and after growth of the epitaxial layers by means of conventional Lang topography, synchrotron white beam and monochromatic beam topography and by means of X-ray specular reflectometry. The topographic investigations confirmed the continuation of the dislocations in the epitaxial deposit on the 8 degrees and 4 degrees off-cut substrates without new extended defects. The important difference occurred in the surface roughness of the epitaxial layers, which increased for higher growth rates. The epitaxial layers grown on 0 degrees off-cut substrates at analogous condition contained usually other SiC polytypes, but the influence of the growth rate on the distribution of the polytypes was observed.