State of the art in the modelling of SiC sublimation growth

Different computational tools have helped to provide additional information on the sublimation growth of SiC single crystals by the modified-Lely meth od. The modelling work was motivated by the need of a better control of the local temperature field inside the crucible. Because there is an environme nt of strong thermal radiation in which the SiC boule growth process occurs . hear transfer must therefore be coupled with gaseous species transport an d reactivity. This highly coupled model must take into account all geometri c modifications in crucibles which strongly influences the crystal growth p rocess. Local thermochemical equilibrium linked to heat and mass transfer i s the model proposed in this paper to give the magnitude of the growth rate and the shape of the crystal. This modelling field is still too young to p ropose a software package including all modelling aspects and a reliable ma terial database. However. some parts of the modelling work have reached mat urity like electromagnetic heating and thermal modelling coupled with simpl ified chemical models. We show in this paper selected examples in order to demonstrate the types of information which can be routinely available by si mulation and how to approach defect formation from a macroscopic point of v iew. Minor geometric modifications of the holes for pyrometric measurements drastically change the magnitude of thermal gradients in the crucible. Geo metric modifications of the crucible change the computed crystal shapes. Th e calculated results complete the experimental knowledge by a quantificatio n of the local macroscopic fields. (C) 1999 Elsevier Science S.A. All right s reserved.