  We investigate the role of electron-phonon scattering and gate bias in
degrading the drive current of nanotube MOSFETs. Our central results are: (i)
Optical phonon scattering significantly decreases the drive current only when
gate voltage is higher than a well-defined threshold. It means that elastic
scattering mechanisms are most detrimental to nanotube MOSFETs. (ii) For
comparable mean free paths, a lower phonon energy leads to a larger degradation
of drive current. Thus for semiconducting nanowire FETs, the drive current will
be more sensitive than carbon nanotube FETs because of the smaller phonon
energies in semiconductors. (iii) Radial breathing mode phonons cause an
appreciable reduction in drive current.
