Abstract: 4H-SiC crystallization from Si-C solution in electric current-controlled liquid phase epitaxy was investigated. The dependence of growth speed on a DC current shows that dissolution/growth is controlled by the electric current without altering temperature gradient in the furnace. Application of an electric current leads to reduction of growth speed with negative polarity and enhancement of growth speed with positive polarity. The variation of the growth speed with a DC current density has been explained by the combination of the effects of electromigration of C solute and Joule heating.
Abstract: For bulk growth of SiC crystal with higher quality, it is important to control the temperature distribution inside the crucible. We have performed numerical calculations of the temperature distribution inside the growing crystal, and discussed the relationship between the calculated sheer stress and the basal plane dislocation densities. We found that growth with lower basal plane dislocation defect densities, specifically at the front edge of the crystal, is possible by lowering the temperature gradient toward the growth direction.
Abstract: SiC crystal ingots were grown on 6H-SiC dual-seed crystal with different surface properties by a PVT (Physical Vapor Transport) technique. And then SiC crystal wafers sliced from the SiC ingots were systematically investigated in order to find out the dependence of surface properties for seed on the polytype formation. While n-type SiC crystals exhibiting the 4H polytype were grown on seed crystal having high root-mean-square (rms) value, 6H-SiC crystals were grown on seed having lower rms value. However, 6H polytype was maintained on on-axis and off-axis seeds during the entire growth period. The crystal quality of 6H-SiC single crystals grown on on-axis seed were revealed to be slightly better than that of 6H-SiC crystal grown on off-axis seed.
Abstract: We investigated the dislocation behaviors during the solution growth on Si-face and C-face off-axis 4H-SiC seed crystals by using synchrotron X-ray topography. On Si-face, almost all threading screw dislocations (TSDs) and threading edge dislocations (TEDs) are converted into Frank-type defects and basal plane dislocations (BPDs), respectively. On the other hand, on C-face, TSDs were hardly converted. Some of TEDs were converted to BPDs and BPD-TED reconversion was often occurred. Therefore, to reduce density of threading dislocations in the grown crystal, it is better to use Si-face off-axis seed crystal.
Abstract: Fluorescent silicon carbide was grown using the fast sublimation growth process on low off-axis 6H-SiC substrates. In this case, the morphology of the epilayer and the incorporation of dopants are influenced by the Si/C ratio. Differently converted tantalum foils were introduced into the growth cell in order to change vapor phase stochiometry during the growth. Fluorescent SiC grown using fresh and fully converted tantalum foils contained morphological instabilities leading to lower room temperature photoluminescence intensity while an improved morphology and optical stability was achieved with partly converted tantalum foil. This work reflects the importance of considering the use of Ta foil in sublimation epitaxy regarding the morphological and optical stability in fluorescent silicon carbide.
Abstract: We have investigated growth rate and surface morphology of 4H-SiC single crystal grown from Si-C solution with various supersaturation levels at growth temperature in the range from 1840 to 2140 °C. The growth rate depends linearly on the amount of supersaturated carbon, irrespective of the growth temperature. This indicates that the growth is limited by the transfer of solute element onto the crystallization front. The adequate condition for stable solution growth are discussed with respect to high growth rate and surface morphology.
Abstract: In this paper, we present for the first time an in-situ 3-D reconstruction of the SiC crystal growth interface using X-ray computed tomography (CT). We show that the shape of the growth interface can be determined with high precision at growth temperatures above 2100 °C in a conventional 3” PVT (physical vapor transport) growth system.
Abstract: 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.
Abstract: 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.