Transport through the interface between a semiconducting carbon nanotube and a metal electrode

We report a numerical study of the tunnel conductance through the Schottky barrier at the contact between a semiconducting carbon nanotube and a metal electrode. In a planar gate model the asymmetry between the p-doped and the n-doped region is shown to depend mainly on the difference between the electrode Fermi level and the band gap of carbon nanotubes. We quantitatively show how the gate/nanotube distance is important to get large on-off ratios. We explain the bend of the current versus gate voltage as the transition from a thermal-activation region to a tunneling region. A good agreement is obtained with experimental results for carbon nanotubes field-effect transistors.