The aim of this work is to study the effect of Ge introduction during the nucleation step on the SiC growth on 4H-SiC on-axis substrate. After 10 minutes surface pretreatment at 1500 C under C 3 H 8 or GeH 4, the grown 3C layer at the same temperature can switch from highly twinned (C 3 H 8) to almost twin-free single domain (GeH 4). However, for too low and too high GeH 4 fluxes, the layers display a mixture of polytype. Keeping the best pretreatment but varying the growth temperature degrades the morphology and changes the polytype of the layer. Preliminary electrical results using C-AFM on the 3C-SiC layer are also presented.