Charge trapping and scattering in epitaxial graphene

The Hall mobility and corresponding density of charge carriers in epitaxial graphene exhibit unexpectedly strong temperature dependence. This behavior is attributed to charge traps in the silicon carbide substrate that have a characteristic binding energy of approximately 70 meV. The electrostatic screening associated with these traps and the corresponding carrier transport behavior are investigated, as is transport at low densities, where the mobility sharply increases. The mobility at high carrier densities can be satisfactorily described by invoking Coulomb and short-range scattering. Scatterer transparency in the long-wavelength limit is suggested to occur in the low density regime, resulting in an abrupt mobility increase.