Quantum Transport in Two-Dimensional WS<sub>2</sub> with High-Efficiency Carrier Injection through Indium Alloy Contacts.

Lau, Chit Siong; Chee, Jing Yee; Ang, Yee Sin; Tong, Shi Wun; Cao, Liemao; Ooi, Zi-En; Wang, Tong; Ang, Lay Kee et al. · ACS Nano · 2020

basic_science · Level V

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Abstract

Two-dimensional transition metal dichalcogenides (TMDCs) have properties attractive for optoelectronic and quantum applications. A crucial element for devices is the metal-semiconductor interface. However, high contact resistances have hindered progress. Quantum transport studies are scant as low-quality contacts are intractable at cryogenic temperatures. Here, temperature-dependent transfer length measurements are performed on chemical vapor deposition grown single-layer and bilayer WS<sub>2</sub> devices with indium alloy contacts. The devices exhibit low contact resistances and Schottky barrier heights (∼10 kΩ μm at 3 K and 1.7 meV). Efficient carrier injection enables high carrier mobilities (∼190 cm<sup>2</sup> V<sup>-1</sup> s<sup>-1</sup>) and observation of resonant tunnelling. Density functional theory calculations provide insights into quantum transport and properties of the WS<sub>2</sub>-indium interface. Our results reveal significant advances toward high-performance WS<sub>2</sub> devices using indium alloy contacts.