  Electronic transport in a carbon nanotube (CNT) metal-oxide-semiconductor
field effect transistor (MOSFET) is simulated using the non-equilibrium Green's
functions method with the account of electron-phonon scattering. For MOSFETs,
ambipolar conduction is explained via phonon-assisted band-to-band
(Landau-Zener) tunneling. In comparison to the ballistic case, we show that the
phonon scattering shifts the onset of ambipolar conduction to more positive
gate voltage (thereby increasing the off current). It is found that the
subthreshold swing in ambipolar conduction can be made as steep as 40mV/decade
despite the effect of phonon scattering.
