Formation and suppression of misoriented grains in 6H-SiC crystals

The availability of high-quality silicon carbide (SiC) single crystals with large diameter is a key issue in the development of the full potential of SiC-based device technology. The formation and suppression of misoriented grains (MGs) in the marginal area of as-grown 6H-SiC single crystals are mainly discussed in this paper. The polytype of the MGs is identified to be mainly 6H-SiC by Raman spectroscopy and XRD. Results of modulation growth, in which different stages are decorated with nitrogen, reveal that the growth rate of MG is higher than that of the matrix. Owing to the MG orientation deviating from [0001], no micropipe has been observed in the etched MG samples. At the same time, there exist many thermal decomposition cavities (TDCs) at the initial growth stage, which indicates that the MG may result from a TDC. Based on this possible formation process, a method via sputtering carbon film on C-terminated (0001) 6H-SiC surface for eliminating TDCs is proposed, which may be helpful to suppress formation of MGs, hence to effectively grow SiC crystals with high quality and large diameter by moderate controls of critical growth conditions in the PVT technique.