Papers by Author: Joon Suk Song

Abstract: We examined the influence of thermal treatment of high-purity SiC powder on 6H-SiC crystal growth. The doping concentration was decreased by increasing either thermal treatment temperature or time. It was also found that the defects such as micropipes and planar cavities were generated under relatively long treatment time (13 hours), because SiC powders were significantly graphitized. A 6H-SiC crystal grown by using SiC source treated at 2100oC for 6 hours revealed the best result with relatively low micropipes. For the effects of thermal treated sources on the improvement of crystallinity, it could be explained that both the amount of alpha phase transformed from high-purity beta-SiC powder and the elimination of porous powders in SiC powder had an influence on the removal of silicon droplets, resulting in higher Si vapor pressure at the initial growth stage.

Abstract: The variation of nitrogen doping concentration was systematically investigated with respect to the amount of silicon powder added to the SiC powder for growing n-type 6H-SiC single crystal by the sublimation method. To change intentionally the Si content in the SiC powder, 0wt% to 2wt% of a silicon powder was added to first-thermal treated SiC powder and the mixed powder was treated again at 1800oC for 3 hours to eliminate excess free-metallic silicon. Nitrogen doped 6H-SiC single crystals were grown by using 2nd-thermal treatment SiC powder at fixed N2/(Ar + N2) (3%). The nitrogen doping concentration of 6H-SiC crystals increased with increasing Si content in the SiC powder. In this work, we could identify that the additional silicon powder in SiC powder plays a role in the enhancement of nitrogen doping in 6H-SiC crystals grown by the sublimation method.

Abstract: We present experimental results with regard to the evaluation of growth-induced polytype domains in 6H-SiC crystals grown by sublimation method and these domains are characterized by using the polarized optical microscopy and micro-Raman spectroscopy. The polytype domains of reverse triangular are generated by local variation of temperature along cdirection and spread-wing shapes normally occurred forming micropipes in many cases. These polytype domains may be generated due to the local variation of supersaturation and/or temperature at central position during crystal growth. In this work, we try to elucidate the origin and mechanism responsible for growth-induced polytype domains.

Abstract: We examined the formation of poly-crystals and polytypes under the point of view applying various powder phases. 6H-SiC single crystal was easily grown by using the green (α-SiC) powder, while the poly-crystals were generated when β-SiC powder was utilized. The method of mixed β-SiC and carbon powder and of graphite pipe inserted in β-SiC powder were applied to overcome the generation of poly-crystals, respectively. It was confirmed that the occurrence of poly-crystals in 6H-SiC crystal was successfully suppressed by C-rich environment.