Ambipolar leakage suppression in electron–hole bilayer TFET: investigation and analysis

Abstract

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 $$\hbox {M}_{1}$$ as overlap gate, $$\hbox {M}_{2}$$ 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 $$I_{\mathrm{ON}}/I_{\mathrm{OFF}}$$ ratio is increased by more than one order at $$V_\mathrm{{GS}}=V_{\mathrm{DS}} =1.0$$ V as compared to the conventional Si EHBTFET. The performance is improved further by employing asymmetric underlaps ( $$\hbox {Lgs}\ne \hbox {Lgd}$$ ) 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 $$0.23~\upmu \hbox {A}/\upmu \hbox {m}$$ (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 $$I_{\mathrm{ON}}/I_{\mathrm{OFF}}\,\hbox {ratio}~>10^{9}$$ (two orders higher) is achieved at $$V_{\mathrm{DS}} =V_{\mathrm{GS}} =1.0~\hbox {V}$$ in the proposed structure 2 in comparison with the conventional one.