  In this paper, we have presented the impact of the gate leakage through thin
gate dielectrics (SiO2 and high-\k{appa} gate dielectric) on the subthreshold
characteristics of the tunnel field effect transistors (TFET) for a low
operating voltage of 0.5 V. Using calibrated two-dimensional simulations it is
shown that even for such a low operating voltage, the gate leakage
substantially degrades several subthreshold parameters of the TFET such as the
off-state current, minimum subthreshold swing and average subthreshold swing.
While the drain-offset as well as the short-gate are effective methods for
reducing the gate leakage, we show that if the gate tunneling leakage is not
considered, even for these two methods, the overall TFET off-state current will
be significantly underestimated. Our results demonstrate the need to carefully
account for the gate leakage in the design of TFETs just as it is done for the
conventional nanoscale MOSFETs.
