Hole-channel conductivity in epitaxial graphene determined by terahertz optical Hall-effect and midinfrared ellipsometry*

We report non-contact, optical determination of free-charge carrier mobility, sheet density, and effective mass parameters in epitaxial graphene at room temperature using terahertz and midinfrared ellipsometry and optical Hall-effect (generalized ellipsometry in magnetic fields) measurements. The graphene layers are grown on Si- and C-terminated semi-insulating 6H silicon carbide polar surfaces. Data analysis using classical Drude functions and multilayer modeling render the existence of a $p$-type channel with different sheet densities and effective mass parameters for the two polar surfaces. The optically obtained parameters are in excellent agreement with results from electrical Hall effect measurements.