2D Tunnel Field Effect Transistors (FETs) with a Stable Charge-Transfer-Type p$^+$-WSe$_2$ Source

TL;DR

This paper demonstrates the development of stable, highly doped p$^+$-WSe$_2$ source materials for 2D TFETs using charge transfer doping, enabling clear tunneling and negative differential resistance behaviors.

Contribution

It introduces a stable charge transfer doping method for p$^+$-WSe$_2$ sources, advancing 2D TFET fabrication with improved doping stability and device performance.

Findings

Successful stabilization of p$^+$-WSe$_2$ on h-BN substrate.

Observation of band-to-band tunneling at low temperatures.

Clear negative differential resistance behavior in fabricated TFETs.

Abstract

Two-dimensional (2D) materials are highly promising for tunnel field effect transistors (TFETs) with low subthreshold swing and high drive current because the shorter tunnel distance and strong gate controllability can be expected from the van der Waals gap distance and the atomically sharp heterointerface formed independently of lattice matching. However, the common problem for 2D-2D TFETs is the lack of highly doped 2D materials with the high process stability as the sources. In this study, we have found that p+-WSe2 doped by charge transfer from a WOx surface oxide layer can be stabilized by transferring it onto a h-BN substrate. Using this p$^+$-WSe$_2$ as a source, we fabricate all-solid-state 2D-2D heterostructure TFETs with an Al2O3 top gate insulator, i.e., type-II p$^+$-WSe$_2$ /MoS$_2$ and type-III p$^+$-WSe$_2$ /WSe$_2$. The band-to-band tunneling and negative differential resistance trends are clearly demonstrated at low temperatures. This work suggests that high doped 2D crystal of the charge transfer type is an excellent choice as sources for TFETs.