The surfaces of 4H- and 6H-type substrates were investigated by means of transmission electron microscopy and X-ray topography. Unfilled micropipes (hollow-cored pure screw dislocations extending along [00•1] directions) were observed. Substrates which had been processed by using a micropipe-filling method appeared to possess a lower density of micropipes than did those fabricated without using that process. Initial homo-epitaxial growth of carbide inside the micropipe channels, via liquid-phase epitaxy, appeared to fill (or partially fill) the micropipe core yet retain screw dislocations in closed-core form. Subsequent liquid-phase epitaxial layer growth on these modified substrates retained the continuity of the close-packed atomic stacking of the original substrate. Closed-core screw dislocations from the filled micropipes then transformed into nano-pores, which extended mainly along the [00•1] direction of the substrate, or into grain boundary dislocations. Homo-epitaxial growth into micropipe channels was suggested to produce an incoherent interface between the substrate and filled material, and to produce misfit dislocations in subsequent liquid-phase epitaxial layers.

Structural Investigation on the Nature of Surface Defects Present in Silicon Carbide Wafers Containing Varying Amount of Micropipes M.Shamsuzzoha, S.E.Saddow, T.E.Schattner, L.Jin, M.Dudley, S.V.Rendakova, V.A.Dmitriev: Materials Science Forum, 2000, 338-342, 453-6