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Si-Cr alloy is one of the predominant solvents for rapid solution growth of 4H-SiC crystals. The solubilities of carbon in Si-40 mol%Cr alloy at SiC saturation at 1773-2273 K and in Si-Cr alloys of various chromium contents at 2073 K were measured by equilibrating the Si-Cr alloy with a 4H-SiC single crystal. Carbon solubility in Si-40 mol%Cr alloy increased with temperature from 0.22 mol% at 1773 K to 3.59 mol% at 2273 K. At 2073 K, carbon solubility at SiC saturation increased with the chromium content in the liquid from 0.18 mol% in Si-20 mol%Cr to 16.4 mol% in Si-80 mol%Cr. A thermodynamic analysis of the Si-Cr-C alloy was also conducted. Although the sub-regular solution model is often adopted to estimate phase relations in solution systems, this predicted a carbon solubility in Si-40 mol%Cr at SiC saturation more than two times higher than the measured value. In contrast, a quasi-chemical model that considered the competition between substitutional Si and Cr atoms bonding to interstitial carbon atoms reproduced the activity coef cient of carbon in Si-Cr alloys of 60-100 mol%Si composition, in which the carbon solubility at SiC saturation was less than 1.5 mol%, fairly well. This quasi-chemical model enabled the precise phase relation to be evaluated when designing the solution growth of SiC using a Si-Cr solvent.

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We have grown high-quality long cylindrical (12 mm thick) 4H-SiC bulk crystals by the meniscus formation technique, which was first applied for the solution growth of bulk SiC. It enabled long-term growth by suppressing parasitic reactions such as polycrystal precipitation around the seed crystal. In addition, we could control the growth angle from −22° to 61° by adjusting the meniscus height. The thickness of the grown cylindrical crystals was 12 mm, which is the largest reported until now, and corresponded to a growth rate of 0.6 mm/h. Smooth morphology growth was maintained on the (000-1) C-face. In cross-sectional transmission optical microscopy images, few solvent inclusions and voids were observed. XRD measurements revealed that the FWHM values of the grown crystals were almost the same as those of the seed crystal.

High-speed solution growth using Si-Cr based melt has been performed on on-axis 4H-SiC(0001) at a high temperature of about 2000°C. The maximum growth rate for one-hour growth reaches to 1120 m/h, while the typical growth rate of growth for 2h is about 500 m/h. A large crystal that is about 25 mm in diameter and 1650 m in thickness can be obtained by growth for 5h. The crystal quality is confirmed to be homogeneous by X-ray diffraction and X-ray topography, because FWHM is less than 30 arcsec. Etch pit density of the threading dislocations in the grown crystal is 103-104 cm-2, and that of basal plane dislocation is 2×102-3×103 cm-2. Resistivity of the crystals grown by the solution growth is comparable to those of crystals grown by physical vapor transport technique.