Top- and side-gated epitaxial graphene field effect transistors

Three types of first generation epitaxial graphene (EG) field effect transistors (FET) are presented and their relative merits are discussed. Graphene is epitaxially grown on both the carbon and silicon faces of hexagonal silicon carbide and patterned with electron beam lithography. The channels have a Hall bar geometry to facilitate magnetoresistance measurements. FETs patterned on the Si-face exhibit off-to-on channel resistance ratios that exceed 30. C-face FETs have lower off-to-on resistance ratios, but their mobilities (up to 5000 cm 2 /Vs) are much larger than that for Si-face transistors. Initial investigations into all-graphene side-gate FET structures are promising. Conductivity (left panel) and transport resistances ρ xx and ρ xy of a top gate graphene Hall bar on SiC Si-face, showing a sign reversal of the Hall coefficient at the resistance peak.