The main challenge for tunnel field-effect transistors (TFETs) is achieving high on-current (Ion) and low subthreshold swing (SS) with reasonable ambipolar characteristics. In order to address these challenges, Ge-channel heterostructure TFET with Si source and drain region is proposed, and its electrical characteristics are compared to other TFET structures. From two-dimensional (2-D) device simulation results, it is confirmed that the Si/Ge heterostructure source junction improves Ion and SS characteristics by using the direct band-to-band tunneling current. Furthermore, the proposed structure shows suppressed ambipolar behavior since the Ge/Si heterostructure is used at the drain junction.

In this study, the effects of back-gate bias on the subthreshold swing (S) of a tunnel field-effect transistor (TFET) were discussed. The electrostatic characteristics of the back-gated TFET were obtained using technology computer-aided design (TCAD) simulation and were explained using the concepts of turn-on and inversion voltages. As a result, S decreased, when the back-gate voltage increased; this behavior is attributed to the resultant increase in inversion voltage. In addition, it was found that the on–off current ratio of the TFET increased with a decrease in S due to the back-gate voltage.