Nucleation and subsequent growth of cubic SiC (1 1 1) on Si- and C-faces of nominally on-axis 6H-SiC substrates was investigated. More uniform nuclei and twin boundary distribution was observed when 3C-SiC was grown on the C-face. This was attributed to a lower critical supersaturation ratio. A new type of defects which appear as pits in the C-face 3C-SiC layers related to homoepitaxial 6H-SiC spiral growth was found and described. The evaluation of the growth driving force for both polar faces showed that the homoepitaxial 6H-SiC spirals were not overgrown on the C-face due to low maximum supersaturation ratio. The XRD omega-rocking characterization shows a better structural quality of the 3C-SiC grown on the Si-face, however on the C-face the uniformity over the whole sample was higher. Unintentional doping by N (similar to 10(16) cm(-3)) was slightly higher on the C-face while Al doping was higher (similar to 10(14) cm(-3)) on the Si-face of the grown material, similarly to the doping of hexagonal SiC polytypes. (C) 2012 Elsevier B.V. All rights reserved.