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 demonstra ted using a dual-seed technique to grow on both the C- and Si-face see d 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 und er 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-fac e, and is independent of both polytype and 8 degrees off-axis orientat ion. The addition of more than 15% silicon powder to the SiC sublimati on source resulted in polycrystalline growth. (C) 1996 American Instit ute of Physics.