The propagation behavior of basal plane dislocations from off-oriented 4H-SiC substrates into homoepitaxial layers was investigated using transmission electron microscopy, secondary electron microscopy, and chemical etching. Cross-sectional transmission electron microscopy shows that basal plane dislocations in the substrate were dissociated into pairs of partial dislocations separated by a stacking fault with a width of about 40nm. Near the substrate/epilayer interface, where most of the basal plane dislocations convert to threading edge dislocations, the two partials constrict before converting. Threading edge segments were inclined by about 20° from the c-axis toward the down-step direction. It was concluded that the critical and limiting step of the dislocation conversion process was constriction of the dissociated partials. Growth surface morphology at the emergence point of the basal plane dislocation was imaged using secondary electron microscopy and was thought to play an important role in the constriction.

Direct Observation of Basal-Plane to Threading-Edge Dislocation Conversion in 4H-SiC Epitaxy. S.Chung, V.Wheeler, R.Myers-Ward, C.R.Eddy,  D.K.Gaskill, P.Wu, Y.N.Picard, M.Skowronski: Journal of Applied Physics, 2011, 109[9], 094906