Growth of 6H and 4H silicon carbide single crystals by the modified Lely process utilizing a dual-seed crystal method

The influence of polarity on the SiC crystal growth has been demonstrated using a dual-seed technique to grow on both the C- and Si-face seed simultaneously. For the investigated range of growth conditions, 4H-SiC crystals were grown on the C-face of 6H-SiC seed crystals with on-axis orientation, when the growth rate exceeded 1.2 g/h. We were never able to grow 4H-SiC on the Si-face of 6H- or 4H-SiC seed crystals under these growth conditions. The incorporation of nitrogen is shown to be 2.3 times higher in crystals grown on the C-face than on the Si-face, and is independent of both polytype and 8 degrees off-axis orientation. The addition of more than 15% silicon powder to the SiC sublimation source resulted in polycrystalline growth. (C) 1996 American Institute of Physics.