Micro- and Nano-Scale Electrical Characterization of Epitaxial Graphene on Off-Axis 4H-SiC (0001)

The electrical properties of epitaxial graphene (EG) grown on 8 degrees off-axis 4H-SiC (0001) by annealing at 1600 degrees C in inert gas ambient (Ar) were studied. The sheet resistance of the EG layers (R-sh=740 +/- 50 Omega/sq) and the specific contact resistance of Ni contacts to EG (rho(c)approximate to 6x10(-5) Omega cm(2)) were evaluated on micrometer scale by measurements on transmission line model (TLM) structures. Si3N4 was evaluated as a gate dielectric, showing excellent coverage to EG and a limited effect on its conductivity. The high n-type doping (similar to 10(13) cm(-2)) of EG, as well as the field effect mobility (mu) dependence on n were determined using top gated field effect transistors (FETs) with Si3N4 gate dielectric. Electron mean free path (l(loc)) and mobility (mu(loc)) were also locally determined, on submicrometer scale, by scanning probe microscopy, showing a broad distribution of values, with the most probable value very similar to the macroscopic carrier mobility mu.