Contact Engineering High Performance n -Type MoTe 2 Transistors

• Published in: Nano letters 2019-09, Vol.19 (9), p.6352-6362
• Main Authors: Mleczko, Michal J, Yu, Andrew C, Smyth, Christopher M, Chen, Victoria, Shin, Yong Cheol, Chatterjee, Sukti, Tsai, Yi-Chia, Nishi, Yoshio, Wallace, Robert M, Pop, Eric
• Format: Article
• Language: English
• ISSN: 1530-6984; 1530-6992
• DOI: 10.1021/acs.nanolett.9b02497

Semiconducting MoTe is one of the few two-dimensional (2D) materials with a moderate band gap, similar to silicon. However, this material remains underexplored for 2D electronics due to ambient instability and predominantly -type Fermi level pinning at contacts. Here, we demonstrate unipolar -type MoTe transistors with the highest performance to date, including high saturation current (>400 µA/µm at 80 K and >200 µA/µm at 300 K) and relatively low contact resistance (1.2 to 2 kΩ∙µm from 80 to 300 K), achieved with Ag contacts and AlO encapsulation. We also investigate other contact metals, extracting their Schottky barrier heights using an analytic subthreshold model. High-resolution X-ray photoelectron spectroscopy reveals that interfacial metal-Te compounds dominate the contact resistance. Among the metals studied, Sc has the lowest work function but is the most reactive, which we counter by inserting monolayer h-BN between MoTe and Sc. These metal-insulator-semiconductor (MIS) contacts partly de-pin the metal Fermi level and lead to the smallest Schottky barrier for electron injection. Overall, this work improves our understanding of n-type contacts to 2D materials, an important advance for low-power electronics.