The strong enhancement of stacking-fault formation in 4H-SiC by heavy N-doping was investigated. Localized but severe deformation bands were observed in certain regions of 4H-SiC wafers that had undergone high-temperature processing. By using a combination of dynamic secondary ion mass spectroscopy and conventional, weak-beam and high-resolution transmission electron microscopy, the affected regions of the wafers were found to have a much higher concentration of N and to contain a high density of stacking faults. In contrast, in the non-affected regions of the wafers, the N concentration was lower and no lattice defects could be observed by transmission electron microscopy; thus indicating that the severely deformed morphology of the affected regions was due to the high stacking-fault content. The stacking faults in the affected regions were found to be invariably double-, and not single-layered, and formed via the glide of 2 leading partial dislocations on adjacent (00▪1) planes. The occurrence of stacking faults during deformation testing of heavily N-doped 4H-SiC was studied by combining optical microscopy, high-resolution and weak-beam transmission electron microscopy. The generated faults were found to be double-layered as well. It was noted that, in neither type of experiment, were trailing partials observed. It appeared that the stacking faults were not in the form of ribbons bounded by leading and trailing partials, but rather in the form of faulted loops on 2 adjacent planes with each loop bounded by a leading Shockley partial having the same Burgers vector. The results of the observations were explained in terms of the stabilization of double-layer stacking faults when the Fermi level of the faulted crystal was pushed up, by N doping, to above the stacking fault energy level.

Nitrogen Doping and Multiplicity of Stacking Faults in SiC. P.Pirouz, M.Zhang, H.M.Hobgood, M.Lancin, J.Douin, B.Pichaud: Philosophical Magazine, 2006, 86[29-31], 4685-97