  Tunneling field-effect transistors (TFETs) have gained a great deal of recent
interest due to their potential to reduce power dissipation in integrated
circuits. One major challenge for TFETs so far has been achieving high drive
currents, which is a prerequisite for high-performance operation. In this paper
we explore the performance potential of a 1D TFET with a broken-gap
heterojunction source injector using dissipative quantum transport simulations
based on the nonequilibrium Green's function formalism, and the carbon nanotube
bandstructure as the model 1D material system. We provide detailed insights
into broken-gap TFET (BG-TFET) operation, and show that it can indeed produce
less than 60mV/decade subthreshold swing at room temperature even in the
presence of electron-phonon scattering. The 1D geometry is recognized to be
uniquely favorable due to its superior electrostatic control, reduced carrier
thermalization rate, and beneficial quantum confinement effects that reduce the
off-state leakage below the thermionic limit. Because of higher source
injection compared to staggered-gap and homojunction geometries, BG-TFET
delivers superior performance that is comparable to MOSFET's. BG-TFET even
exceeds the MOSFET performance at lower supply voltages (VDD), showing promise
for low-power/high-performance applications.
