Jakub Jadwiszczak, Jeffrey Sherman, David Lynall, Yang Liu, Boyan Penkov, Erik Young, Rachael Keneipp, Marija Drndić, James C. Hone, and Kenneth L. Shepard, “Mixed-Dimensional 1D/2D van der Waals Heterojunction Diodes and Transistors in the Atomic Limit,” ACS Nano 2022 16 (1), 1639-1648

Inverting a semiconducting channel is the basis of all field-effect transistors. In silicon-based metal-oxidesemiconductor field-effect transistors (MOSFETs), a gate dielectric mediates this inversion. Access to inversion layers may be granted by interfacing ultrathin low-dimensional semiconductors in heterojunctions to advance device downscaling. Here we demonstrate that monolayer molybdenum disulfide (MoS2) can directly invert a single-walled semiconducting carbon nanotube (SWCNT) transistor channel without the need for a gate dielectric. We fabricate and study this atomically thin one-dimensional/two-dimensional (1D/2D) van der Waals heterojunction and employ it as the gate of a 1D heterojunction field-effect transistor (1D-HFET) channel. Gate control is based on modulating the conductance through the channel by forming a lateral p−n junction within the CNT itself. In addition, we observe a region of operation exhibiting a negative static resistance after significant gate tunneling current passes through the junction. Technology computer- aided design (TCAD) simulations confirm the role of minority carrier drift-diffusion in enabling this behavior. The resulting van der Waals transistor architecture thus has the dual characteristics of both field-effect and tunneling transistors, and it advances the downscaling of heterostructures beyond the limits of dangling bonds and epitaxial constraints faced by III−V semiconductors.