No abstract

The etching mechanism of SiC single crystals by molten KOH has been investigated. The etching process is significantly affected by the etching ambience: the etching rate is greatly reduced by a nitrogen gas purge. This result clearly suggests an essential role of dissolved oxygen in the melt. SiC{0001} surfaces show a large surface polarity dependence, where the etching rate of SiC(0001)C is about four times larger than that of SiC(0001)Si. The etching rate of SiC(0001)C exhibits an Arrhenius type temperature dependence with an activation energy of 15-20 kcal/mol. The obtained activation energy and selectivity between the (0001)C and the (0001)Si surfaces are quite similar to those for thermal oxidation, which implies that the surface oxidation process occurs during molten KOH etching of SiC and is the rate-limiting step for the etching. We have conducted a comparative study of molten KOH etching with thermal oxidation in regard to the crystal orientation, polytype and carrier concentration dependence.

No abstract

Polytype-controlled crystal growth of SiC was carried out by using a sublimation method. Production yields as high as 80% and 85% for 4H and 6H single crystals were obtained, respectively. We observed in x-ray diffraction pattern of SiC that space-group-forbidden peaks appear periodically among (000l) peaks. Their intensity is strong enough to be distinguished. These peaks represent the periodicity along the c axis of each polytypic modification of SiC. X-ray diffractometry using these peaks is quite useful and easy for a clear identification of the SiC polytypes.

No abstract