A Novel Tunnel FET Design With Stacked Source Configuration for Average Subthreshold Swing Reduction

In this paper, a novel heterostacked tunnel FET (HS-TFET) is proposed for steeper average subthreshold swing (SS). Different from conventional TFETs, HS-TFETs owns a stacked source configuration consisting of an upper source layer with a relatively larger bandgap material and an underlying source layer with smaller bandgap materials. Since smaller bandgap materials exhibit much higher band-to-band tunneling efficiency, the underlying layer of HS-TFET could provide extra drain current increment with increasing gate voltage, and thus effectively improve the subthreshold characteristics for steeper average SS. The simulation results show that the proposed Si-Ge-based HS-TFET can achieve much steeper average SS (25 mV/decade) than conventional Si TFET (42 mV/decade), exhibiting more than one decade higher I60 without leakage current degradation.