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 (ION) is 69 mu A/mu 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 ION 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).