Performance Booster for Vertical Tunnel Field-Effect Transistor: Field-Enhanced High- $\kappa $ Layer

Abstract

A germanium-source vertical tunnel field-effect transistor with a field-enhanced high- $\kappa $ layer (FEHL-VTFET) is proposed to improve the device performance. The FEHL-VTFET takes advantage of bandgap engineering as well as field-enhancing engineering (i.e., a strong fringing electric field is used in the source region). The ON-state drive current ( $I_{\sc {\mathrm{ ON}}})$ is $69~\mu \text{A}/\mu \text{m}$ at $V_{DS} = V_{GS} =0.5$ V, and is 20 times higher than that of a germanium-source VTFET without the FEHL. The average subthreshold slope (SS) is 37.5 mV/decade at 300 K. The large permittivity constant of FEHL enhances both the $I_{\sc {\mathrm{ ON}}}$ and the average SS. Finally, the drain-induced barrier thinning is alleviated, because the use of an FEHL with a high- $\kappa $ layer can induce a stronger electric field in the source region; therefore, the tunneling generation rate is mainly determined by the gate voltage (and not by the drain voltage).