Electrical properties of the graphene/4H-SiC (0001) interface probed by scanning current spectroscopy

The current transport across the graphene/4H-SiC interface has been investigated with nanometric lateral resolution by scanning current spectroscopy on both epitaxial graphene (EG) grown on (0001) 4H-SiC and graphene exfoliated from highly oriented pyrolytic graphite deposited on the same substrate [deposited graphene (DG)]. This study reveals that the Schottky barrier height (SBH) of EG/4H-SiC (0.36 +/- 0.1 eV) is similar to 0.49 eV lower than the SBH of DG/4H-SiC (0.85 +/- 0.06 eV). This result is discussed in terms of the Fermi-level pinning similar to 0.49 eV above the Dirac point in EG due to the presence of positively charged states at the interface between the Si face of 4H-SiC and the carbon-rich buffer layer, which is the precursor for EG formation.