  We report on a new computational model to efficiently simulate carbon
nanotubebased field effect transistors (CNT-FET). In the model, a central
region is formed by a semiconducting nanotube that acts as the conducting
channel, surrounded by a thin oxide layer and a metal gate electrode. At both
ends of the semiconducting channel, two semi-infinite metallic reservoirs act
as source and drain contacts. The current-voltage characteristics are computed
using the Landauer formalism, including the effect of the Schottky barrier
physics. The main operational regimes of the CNT-FET are described, including
thermionic and tunnel current components, capturing ambipolar conduction,
multichannel ballistic transport and electrostatics dominated by the nanotube
capacitance. The calculations are successfully compared to results given by
more sophisticated methods based on non-equilibrium Green's function formalism
(NEGF).
