Growth of nitrogen-doped SiC boules by halide chemical vapor deposition

A novel halide chemical vapor deposition process has been developed for growth of single crystal 6H and 4H SiC boules. This process takes advantage of the thermal stability of halogenated precursors and a unique reactor design to produce SiC crystals up to 75 mm in diameter at growth rates up to 250 mm/h. Growth rate was significantly improved by using CH4 instead of C3H8 as the carbon source gas. Growth of the 6H and 4H polytypes was evaluated as a function of seed polytype, off-cut and surface polarity at a growth temperature of 2020 °C, which is well above typical epitaxy conditions and well below typical sublimation growth conditions. The effect of the substrate and nitrogen flow rate on nitrogen incorporation were characterized by secondary ion mass spectrometry. Radial uniformity of doping was assessed by mercury probe capacitance-voltage measurements. Bulk crystals with an average boron concentration of 1.5e15 atoms/cm3 and nitrogen doping level above 1.0e19 atoms/cm3 were readily achieved. High-resolution X-ray diffraction showed that growth of the 4H polytype requires growth on the carbon face of 4H seed crystals.