2D transient viscoplastic model for dislocation generation of SiC by PVT method

Abstract

SiC crystal grown by PVT method has attracted worldwide research attention and it has been successfully produced under various growth conditions, such as growth temperature, pressure, and growth chamber geometry. However, the dislocation multiplication in SiC crystal grown by PVT method are generated by excessed thermal stresses caused by the nonuniform temperature field in the SiC ingot. A 2 dimensional transient finite element model based on the Haasen-Sumino viscoplastic constitutive model (HAS) is developed to evaluate the dislocation densities generated in the SiC crystal grown by PVT method. The dislocation densities generated in the PVT process is the major parameter for the evaluation of final product. The result shows that the maximum dislocation density is about 1.8 × 107 m-2 when the temperature gradient equals -340/90,000 K/s, while it increases to 2.4 × 107 m-2 when the temperature gradient increases to -640/90,000 K/s.