Channel Length Scaling Effects in Graphene Field-Effect Transistor

We present measurement and analysis of the current-voltage characteristics in the high-bias regime of graphene field-effect transistors of different channel lengths. The devices are fabricated with a gate dielectric process based on a polyvinyl alcohol adsorption layer, enabling reliable top-gates with the highest reported efficiency. Device characteristics are strongly determined by velocity saturation of the carriers, the zero-bandgap density-of states, contact doping, and tunneling. Contact doping strongly reduces the effective channel length in the absence of ``spacer'' between the gated channel region and the contacts. Surface polar optical phonon scattering determines saturation velocities down to short channel lengths. At the shortest channel lengths, band-to-band tunneling degrades device output conductance and transconductance.