Low dislocation density and even micropipe free substrates open up a great opportunity to produce high quality epitaxial layers. The epi-layer will become more sensitive to the epitaxial process itself and less dependent on varying substrate quality. Results presented here indicate a strong dependence of the epitaxial layers' growth mode and surface roughness on the substrates' dislocations and domain structure. Thick epitaxial layers grown on near on-axis wafers, both C-face and Si-face, show very similar growth behaviors as for physical vapor transport (PVT) grown crystals. The mix between step-flow and dislocation driven growth on near on-axis C-face chemical vapor deposition (CVD) grown epi-layers (30 μm thick) is resulting in a as smooth, and measured surface roughness is as low, as for growth on 8o off-axis substrates.
Surface roughness, Ra, measured on a 50 μm thick epitaxial layer, grown on a low EPD (1E+4 cm-2) 8o off-axis micropipe free substrate, was as low as 1.0 nm (2.98x2.32 mm area).