The surfaces of 4H- and 6H-type substrates, which were processed with and without liquid-phase epitaxy to fill micro-pipe defects, were investigated by means of transmission electron microscopy and X-ray topographic techniques were used to determine the status of existing unfilled and filled micro-pipes. The unfilled micro-pipes were hollow-core pure screw dislocations which extended along the [00▪1] direction of the hexagonal crystal. Substrates which were processed using the micro-pipe filling process appeared to contain a lower density of micro-pipes than did those which were fabricated without any micro-pipe filling process. The initial homo-epitaxial growth of SiC within the micro-pipe channels, by using liquid-phase epitaxy techniques, appeared to fill or partially fill the micro-pipe core but probably retained 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, with closed-core screw dislocations from the filled micro-pipes transforming into a nano-pore which extended mainly along the [00▪1] direction of the substrate, or a grain boundary dislocation. Homo-epitaxial growth into micro-pipe channels was suggested to produce an incoherent interface between the substrate and filled material, and produced misfit dislocations in the subsequent liquid-phase epitaxial layer.

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