a Qualitative transfer characteristics of our 2D–2D TFET and its built-in MOSFET together with the sought after characteristic of the DT FET. Ideally, the dual transport FET should turn ON following the steep TFET curve, and then reach the thermionic ION current provided by the WSe2 MOSFET. b Transfer characteristics of the WSe2 FET and WSe2/SnSe2 TFET with optimized threshold voltages, so to obtain VTh,TFET > VTh,MOSFET. The resulting DT transfer characteristics inherits the advantages of the two devices. All the curves are measured at VD = 500 mV. c Transconductance efficiency of the DT FET and its constituting devices. While not reaching the peak transconductance value of the WSe2/SnSe2 heterojunction, the DT FET maintains better performance of the MOSFET for all the output current range, outperforming also the TFET at large current values. d Direct comparison of the substhreshold slope as a function of output current for the DT FET and the base components. Similarly to the transconductance efficiency, the DT FET exhibits a minimum point subthreshold slope larger than the TFET, but it outperforms the WSe2 MOSFET over the entire range of output current and maintains steeper characteristic than the heterojunction FET for large ID.