An investigation was made of the origin of micropipe defects using 6H-type single crystals which had been grown under conditions involving normal or Si-added atmospheres. The micropipe densities were zero, or equal to 22.5/cm2, for representative areas of crystals which had been grown under normal and Si-added atmospheres, respectively. A new Vickers indentation technique was used to expose the inner surface of a micropipe for Auger electron spectroscopic analysis. This revealed that no specific evidence for Si-droplets was to be found at the starting point of micropipes in 6H-type single crystals which were grown under Si-added atmospheres. Although a large number of small-angle boundaries and screw dislocations were observed in the region around micropipe defects, even in a low micropipe-density (1/cm2) crystal, the screw dislocation densities were of the order of 600/cm2 in other regions.

Investigation of the Origin of Micropipe Defects A.Okamoto, N.Sugiyama, T.Tani, N.Kamiya: Materials Science Forum, 2000, 338-342, 441-4