Integrated Tunnel FETs (TFETs) are devices in which the gate controls the tunneling currents to the drain. TFETs are known to exhibit steep subthreshold slope and temperature independent operation, which makes the device suitable for low voltage applications.
Symmetric TFETs have some disadvantages, though. For example, symmetric TFETs have low ON current because of a long conduction path. They also exhibit increased junction capacitance. Also, in certain types of TFETs with a TSi-pad, there may be a high OFF current if the TSi-pad is not lightly doped. This, in turn, increases the series resistance of the device. Moreover, OFF state leakage may be an issue if band-gap engineering is not done properly.