Various liquid-phase epitaxial growth methods (dipping, sessile drop) were used to analyze the evolution of hollow-core defects in PVT crystals during liquid-phase epitaxy. Experiments were performed on the (00•1)/(00•¯1) surfaces of 6H- and 4H-type wafers, using high Ar pressures. Processing at a low supersaturation permitted the evaluation of the early stages of defect development, and long-term experiments (of up to 6h) were used to analyze the stability of defect transformation. Hollow macro-defects which were 10 to 50μm in diameter were found to be very unstable in a Si melt and were already filled at super saturations close to zero, when growth within the core occurred due to the Gibbs-Thomson effect. The resultant structures were found to contain a number of dislocations and micropipes. The elimination of screw-dislocation based micropipes required a higher supersaturation; which could be established by a large temperature difference between the epitaxial surface and the C source. Micropipes were observed to decompose into individually acting non-hollow core dislocations. Following decomposition, the activity of a growth center based upon a micropipe was usually reduced. As a result, a new center could dominate the growing surface and make healed micropipes completely invisible.

Micropipe and Macrodefect Healing in SiC Crystals during Liquid Phase Processing. B.M.Epelbaum, D.Hofmann, U.Hecht, A.Winnacker: Materials Science Forum, 2001, 353-356, 307-10