Papers by Author: Akinori Seki

Abstract: Diffusion of transition metals in 4H-SiC has been investigated by secondary ion mass spectroscopy using epilayers and substrates implanted with titanium (Ti), chromium (Cr), iron (Fe), or nickel (Ni). In the epilayers, Cr, Fe, and Ni atoms have diffused by argon (Ar) annealing at 1780°C for 30 min. In n⁺ substrates, the diffusivity of the metals is smaller than that in the epilayers, and only Ni has diffused by the annealing. By the Ar or helium implantation following the implantation of transition metals, diffusion of transition metals can be successfully suppressed.

Abstract: 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.

Abstract: In this study, we have investigated N2O oxidation of various off-angled 4H-SiC (0001) epilayers and characterized the properties of MOS interfaces. The oxide thickness almost linearly increases with increasing off-angle. Oxidation on highly off-angled (0001) 4H-SiC is faster than that on 8o off-axis (0001). The off-angle dependence of Dit is very small for the MOS capacitors in the off-angle range from 8o to 30o. The depth profiles of carbon and nitrogen atoms near the MOS interface on 15o off-axis 4H-SiC(0001) are similar to those on 8o off-axis (0001).