Sakiko Kawanishi

Solution Growth of Silicon Carbide Using Fe–Si Solvent

In this paper, we describe the use of liquid Fe–Si alloy as the solvent for the solution growth of silicon carbide (SiC). Iron was chosen owing to the high solubility of carbon in molten iron. The crystal growth of SiC from Fe–40 mol % Si solvent on a seed crystal wafer of 6H- or 4H-SiC was carried out at 1,623–1,723 K using induction heating. The growth rate of SiC was obtained to be 90–260 µm/h. Furthermore, Raman spectroscopy revealed homo epitaxial growth on both 6H- and 4H-SiC under the experimental conditions used. Thus, the Fe–Si solvent was found to be effective for the rapid solution growth of SiC.

Real-time observation of the interface between SiC and a liquid alloy and its application to the dissolution behavior of SiC at 1573 K

Real-time observation of the high temperature interface between silicon carbide (SiC) and liquid alloy is indispensable to optimize the conditions for producing high quality SiC crystals by the solution growth method. In this work, real-time observation of the interface was established by using the interference observation to measure the height profile of the interface. The temperature dependence of the refractive index of 4H-SiC was measured up to 1773 K. The height measurement was then carried out for the SiC/alloy interface at 1573 K. From interference observation, bunched step heights of less than 10 nm were measured. The developed technique was applied for the real-time observation of dissolution behavior of SiC into molten Fe-Si alloy at 1573 K. The dissolution kinetics was discussed in terms of carbon mass transfer in the solution and interfacial reaction.

Real-Time Observation of High Temperature Interface between SiC Substrate and Solution during Dissolution of SiC

Precise morphological control of the interface between SiC and solution during the solution growth of SiC is crucial for obtaining high quality crystals with fewer defects and less step bunching. In this paper, a new technique for real-time observation of the high temperature interface between SiC and solution through the back surface of SiC was developed by focusing on the “wide” bandgap of SiC. Real-time observation of the interface during dissolution of SiC into an Fe-Si solvent alloy was carried out using a digital microscope, and the submicron-height structure of the solid-liquid interface was clearly observed at up to 1773 K. Interface morphologies, such as numerous hexagonal pits which were present at the initial stage of dissolution, followed by preferential dissolution in the lateral direction, were observed.

Fundamental study for solvent growth of silicon carbide utilizing Fe-Si melt

Fe-Si melt is a candidate for use as an alloy solvent for rapid liquid phase growth of SiC because of the high solubility of carbon in molten iron. In this work, the equilibrium phase relationship between SiC and the liquid phase of the Fe-Si-C system was investigated at 1523 K by the phase equilibration technique, and was further studied with the thermodynamic calculation. It was found that Fe- 36 mol% Si melt equilibrates with SiC at the temperature and possesses the higher carbon solubility than silicon-based melt. The first trial of the SiC crystal growth experiment was then carried out with Fe- 36 mol% Si melt by means of temperature difference method, and formation of SiC layer was obtained on the graphite substrate. Accordingly, it was found possibility for rapid growth of SiC by the solvent growth method with Fe- 36 mol% Si melt.

Investigation of Solution Growth of SiC by Temperature Difference Method Using Fe-Si Solvent

This paper describes the solution growth of SiC by a temperature difference method using an Fe-Si solvent. Crystal growth of SiC from an Fe-40 mol%Si solvent onto a seed wafer of 6H-SiC or 4H-SiC was carried out at 1623 – 1723 K under induction heating. Homo-epitaxial growth on both 6H-SiC and 4H-SiC was identified by Raman spectroscopy, and the SiC growth rate was found to be 90 – 260 μm/h. Experiments were also conducted under resistance heating at 1623 K using conditions which suppressed natural convection. Convective mass transfer in the solution was found to be important for rapid growth of SiC.

Effect of van der Waals interactions on the stability of SiC polytypes

Density functional theory calculations with a correction of the long-range dispersion force, namely, the van der Waals (vdW) force, are performed for SiC polytypes. The lattice parameters are in good agreement with those obtained from the experiments. Furthermore, the stability of the polytypes in the experiments, which show 3C-SiC as the most stable, is reproduced by the present calculations. The effects of the vdW force on the electronic structure and the stability of polytypes are discussed. We observe that the vdW interaction is more sensitive to the cubic site than the hexagonal site. Thus, the influence of the vdW force increases with decreasing the hexagonality of the polytype, which results in the confirmation that the most stable polytype is 3C-SiC.