Defects formation in sublimation grown 6H-SiC single crystal boules

A perfect understanding of the origin of defects in connection with crystal growth conditions is of prime importance for the future of SIC based electronic. In the generally used modified Lely method (M-Lely), the growth takes place by incongruent sublimation from SIC powder on a monocrystalline SiC seed at low pressure and high temperature. We have recently proposed beginning the growth process at the inversed sign of temperature gradient and low argon pressure. In these conditions, nucleation at low temperature is suppressed and sublimation polishing etching takes place. Then the sign of the temperature gradient is slowly inversed to start the growth. The influence of this nucleation step on the nature and density of defects has been studied by structural analysis using X-ray diffraction, optical and electronic microscopy, atomic force microscopy and synchrotron white beam X-ray topography. The results are discussed in the light of our present understanding of the sublimation process. (C) 1997 Elsevier Science S.A.