International audienceThe links between the occurrence of a given silicon carbide (SiC) polytype and crystal growth conditions have been mainly empirically described. Although studies are a little more advanced, a similar description can be applied to point defects and especially dopants in the crystals. We propose a method to determine such links, based on a coupled thermodynamic and mass transport model, where SiC is treated as a solid solution. We implemented such an approach to the case of the seeded sublimation growth process, which is currently the industrial bulk growth process for SiC single crystalline ingots. The computation of both Si and C activities in the SiC crystal, between the SiC-C and SiC-Si two-phase equilibria, allowed first the assessment of the SiC crystal chemistry and second the linking of SiC-C and SiC-Si chemistry with the growth process parameters. We demonstrate that depending on the temperature, pressure and a temperature gradient, the activities of Si and C in the crystals can be described and tuned. The case of cubic polytype (3C-SiC) formation is specifically discussed. Its stabilization requires a high Si activity and a low C activity in the SiC crystal, meaning that the synthesis conditions must be close to the limit at the SiC + Si phase boundary
International audienceWe used numerical and analytical modeling to investigate fluid flow behaviors close to the growing 4H-SiC crystal surface in the top seeded solution growth process. First, we calculated the azimuthal and radial components of the fluid flow in front of the rotation disc. Second, we developed an analytical model describing the interaction between the step flow (of the vicinal crystal surface) and fluid flow components, considering the crystallography of 4H-SiC and introducing a phase parameter. The correlation of both models allows us to describe qualitatively the conditions for which macrosteps form and destabilize. This phenomenological description is in good agreement with the corresponding experimental observations that are also presented in this paper
The carbon distribution and its transport in the liquid from the source to the crystal directly affect the control of parasitic nucleation, the growth front stability, and the growth rate during SiC solution growth. Controlling the carbon transport is one of the key issues for understanding and improving the process. In this paper, numerical modeling by finite element method is used to describe the complex convective flow pattern in the melt. We focus on electromagnetic convection and investigate the effect of coil frequency, keeping a simple and technologically realistic crucible design. We show that below a critical value of frequency, the carbon transport can be controlled by the electromagnetic convection, giving rise to significant growth rate enhancement.
The growth of homoepitaxial layers on off-oriented 6H-SiC substrates proceeds via step flow growth. Such epilayers can exhibit irregularities like step bunching, splicing or crossover of steps. The effects of the substrate off-orientation and growth temperature show an influence on formation of surface irregularities. The mean features seem to be given by the growth mode competition of two-dimensional growth to the step-flow growth.
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