Transistor downscaling by Moore's law has facilitated drastic improvements in information technology, but this trend cannot continue because power consumption issues have pushed Moore's law to its limit. Tunnel field-effect transistors (TFETs) have been suggested to address these issues; however, so far they have not achieved the essential criteria for fast, low-power switches, i.e., an average subthreshold swing over four decades of current (SSave_4dec) below 60 mV/dec and a current of 1-10 μA/μm where the SS is 60 mV/dec (I60). Here, we report a black phosphorus (BP) heterojunction (HJ) TFET that exhibits a record high I60 of 19.5 μA/μm and subthermionic SSave_4dec of 37.6 mV/dec at 300 K, using a key material factor, monolayer hexagonal boron nitride tunnel barrier for the drain contact. This work, demonstrating the influence of the tunnel barrier contact on device performance, paves the way for the development of ultrafast low-power logic circuits beyond CMOS capabilities.
Keywords: black phosphorus; energy efficient transistor; heterojunction; hexagonal boron nitride tunnel barrier; tunnel field-effect transistor.