Influence of Porous Graphite on SiC Crystal Growth: a Numerical Simulation Study.

SiC is the ideal material for RF devices and power devices. Resistance-heated physical vapor transport method is considered a promising way to grow large size (especially 6 and 8 inch) SiC crystals due to its temperature uniformity. In recent years, the introduction of new technique such as the use of porous graphite improved the SiC crystal quality and yield, while there are only a few relatively comprehensive studies on its mechanism. This paper made comprehensive research on the influence of porous graphite on SiC growth system by means of numerical simulation. The crystal growth experiments under numerical simulation conditions have been carried out accordingly. The numerical simulation results show that the porous graphite raises the temperature and temperature uniformity within the powder area, which can strengthen the sublimation of powder. The temperature difference between the powder and the seed inside the crucible is improved and a greater growth driving force is obtained. The effect of decrease of the re-crystallization at powder surface has also been proved. Besides, the porous graphite improves the flow stability across the whole growth process, and assures a stable crystal growth. The C/ Si ratio has been increased under the influence of porous graphite, and thus reduces the probability of phase transition. The crystal shape has also been improved. The subsequent growth experiments verified the conclusions of numerical simulations such as the improvement of flow uniformity, decrease of poly-type transition probability, improvement of crystal shape, etc. The results of this paper have practical significance on comprehending the effecting mechanism of porous graphite and improving the SiC crystal growth conditions for better crystal quality. [ABSTRACT FROM AUTHOR]