Channel Length Scaling of MoS2 MOSFETs

TL;DR

This study explores the electrical transport and short channel effects in ultrathin MoS2 transistors with channels down to 50 nm, highlighting their immunity to short channel effects and identifying contact resistance as a performance bottleneck.

Contribution

It provides experimental insights into the short channel behavior of MoS2 MOSFETs and identifies key factors limiting their performance, such as contact resistance.

Findings

MoS2 transistors show no obvious short channel effects at 100 nm channel length.

High on/off ratio (~10^9) achieved even with 5 nm thick MoS2.

Performance limited by large contact resistance at the Ni/MoS2 interface.

Abstract

In this article, we investigate electrical transport properties in ultrathin body (UTB) MoS2 two-dimensional (2D) crystals with channel lengths ranging from 2 {\mu}m down to 50 nm. We compare the short channel behavior of sets of MOSFETs with various channel thickness, and reveal the superior immunity to short channel effects of MoS2 transistors. We observe no obvious short channel effects on the device with 100 nm channel length (Lch) fabricated on a 5 nm thick MoS2 2D crystal even when using 300 nm thick SiO2 as gate dielectric, and has a current on/off ratio up to ~109. We also observe the on-current saturation at short channel devices with continuous scaling due to the carrier velocity saturation. Also, we reveal the performance limit of short channel MoS2 transistors is dominated by the large contact resistance from the Schottky barrier between Ni and MoS2 interface, where a fully transparent contact is needed to achieve a high-performance short channel device.