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We grew 3 inch thick 4H-SiC epitaxial layers on the substrate Si-face, and attempted warpage reduction. The substrates were coved by grinding their C-face before the epitaxial growth to cancel out the increase in convex warpage due to the epitaxial growth. We found that the amount of convex warpage change was approximately 26 μm, when the thickness of the epitaxial layer was 200 μm. To reduce warpage, we prepared the substrate with concave warpage of about 27 μm by grinding the C-face, whose roughness was 60 nm. Then, we grew an epitaxial layer of 200 μm thickness on this and we succeeded in reducing the warpage to 5 μm. We concluded that the warpage of thick epitaxial layers on the substrates can be reduced by controlling the roughness of the ground back side, in accordance with the estimated amount of warpage change from the objective thickness of the epitaxial layers.

The increase in threading dislocation during the initial stage of physical vapor transport growth of n-type 4H-SiC crystals was evaluated by cross-sectional X-ray topography. Crystals were grown under two different temperature conditions. A significant increase in threading dislocation was observed in crystals grown at a high, not low, temperature. The local strain distribution in the vicinity of the grown/seed crystal interface was evaluated using the electron backscatter diffraction technique. The local nitrogen concentration distribution was also evaluated by time-of-flight secondary ion mass spectrometry. We discuss the relationship between the increase in threading dislocation and the local strain due to thermal stress and nitrogen concentration.

In this work studied has been the fabrication method of columnar-structured Fe thin film for manifestation of a shape anisotropy in Fe–Cr alloy system, in which the phase separation occurs naturally by the thermal treatment. In order to obtain such a columnar structure, we have utilized the phase separation on a Sn-nanoparticle-dispersed Si substrate, by exploiting an excellent metallurgical affinity of Fe and Sn, and moreover we have employed applying an external magnetic field. Resultingly, we have found that the columnar-structured Fe thin films are likely to be formed after annealing. Thus obtained Fe–Cr–Sn thin film was found to exhibit a high shape-magnetic anisotropy, where the out-of-plane coercivity H c⊥ was about 750 Oe, being five times larger than the in-plane coercivity H c|| of about 150 Oe.