Micropipes and polytypism as a source of lateral inhomogeneities in SiC substrates

Structural and electrical inhomogeneities in SiC bulk crystals grown by the modified Lely sublimation method [1] in 〈0001〉 direction are investigated. Inclusions of different polytypes such as 15R in 6H material are observed on a macroscopic as well as a microscopic scale. Their size and number can be associated with the growth rate of the crystal. Beside the familiar micropipes, ‘nanopipes’ were observed by atomic force microscopy. Micropipes and nanopipes form centers of growth spirals related to the growth mechanism of the crystals under study. These micro- and nanopipes are a major source of structural and electrical inhomogeneities of SiC which are discussed in this paper.