Density dependence of the saturated velocity in graphene

The saturated velocity of a semiconductor is an important measure in bench-marking performance for either logic or microwave applications. Graphene has been of interest for such applications due to its apparently high value of the saturated velocity. Recent experiments have suggested that this value is very density dependent and can even exceed the band limiting Fermi velocity. Some of these measurements have also suggested that the scattering is dominated by the low energy surface polar mode of the SiO₂ substrate. Here, we show that the saturated velocity of graphene on SiO₂ is relatively independent of the density and that the scattering is dominated by the high energy surface polar mode of the substrate.