Methods for the reduction of the micropipe density in SiC single crystals

Micropipes are very harmful for SiC devices. Even one micropipe in the active area can destroy a highvoltage SiC device. Therefore, it is necessary to reduce the density of micropipes in SiC single crystals. In the present paper, we proposed methods for reducing micropipes. Restriction of screw dislocations and decrease of inclusions are the key factors to reduce the number of micropipes. (0 0 0 1) Si-face, ð11 20Þ and ð1 100Þ crystal faces acted as growth surface in different experiments. Active carbon was appended to act as carbon source. The crucible and active carbon were subjected to X-ray diffraction investigation before and after growth. The experimental results indicate that the activity of the graphite crucible was low, and it decreased with the progressing crystal growth, which increased the probability of micropipe formation. Appending active carbon can act as ample carbon source for crystal growth. The reduction of micropipes was achieved by the restrained formation of Si liquid phase. Using ð11 20Þ and ð1 100Þ crystal faces as the growth surfaces the generation of micropipes was restricted, as no new micropipe generated on the ð11 20Þ and ð1 100Þ crystal faces. At the same time, the density of edge dislocations is reduced considerably.