Ambipolar leakage suppression in electron hole bilayer TFET: investigation and analysis
In this paper, we propose and simulate two new structures of electron hole bilayer tunnel field effect transistors (EHBTFET) The proposed devices are n heterogate with \hbox {M}_{1}$M1 as overlap gate, \hbox {M}_{2}$M2 as underlap gate and employs a high k dielectric pocket in the drain underlap. Proposed structure 1 employs symmetric underlaps (Lgs Lgd Lu) The leakage analysis of this structure shows that the lateral ambipolar leakage between channel and drain is reduced by approximately three orders, the OFF state leakage is reduced by one order, and the $I_{\mathrm{ON}/I_{\mathrm{OFF}$ION/IOFF ratio is increased by more than one order at $V_\mathrm{{GS}=V_{\mathrm{DS} =1.0$$VGS=VDS=1.0 V as compared to the conventional Si EHBTFET. The performance is improved further by employing asymmetric underlaps \hbox {Lgs}\ne \hbox {Lgd}$LgsLgd) with double dielectric pockets at source and drain, called as proposed structure 2. The pocket dimensions have been optimized, and an average subthreshold swing of 17.7 mV/dec (25.5% improved) over five decades of current is achieved with an ON current of $0.23~\upmu \hbox {A}\upmu \hbox {m}$0.23mA/mm (11% improved) in proposed structure 2 in comparison with the conventional EHBTFET. Further, the parasitic leakage paths between overlap/underlap interfaces are blocked and the OFF state leakage is reduced by more than two orders. A high $I_{\mathrm{ON}/I_{\mathrm{OFF}\hbox {ratio}>10^{9}$ION/IOFFratio>109 (two orders higher) is achieved at $V_{\mathrm{DS} =V_{\mathrm{GS} =1.0~\hbox {V}$VDS=VGS=1.0V in the proposed structure 2 in comparison with the conventional one.