Contact Engineering High Performance n-Type MoTe2 Transistors

Abstract

Semiconducting MoTe2 is one of the few two-dimensional (2D) materials with a moderate band gap, similar to silicon. However, this material remains under-explored for 2D electronics due to ambient instability and predominantly p-type Fermi level pinning at contacts. Here, we demonstrate unipolar n-type MoTe2 transistors with the highest performance to date, including high saturation current (>400 $\mu A/\mu m$ at 80 K and >200 $\mu A/\mu m$ at 300 K) and relatively low contact resistance (1.2 to 2 $k\Omega \cdot \mu m$ from 80 to 300 K), achieved with Ag contacts and AlOx 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 MoTe2 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.

References in corpus (11)

• 2D materials and van der Waals heterostructures
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• Field-Effect Transistors Based on Few-Layered alpha-MoTe_2
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• van der Waals Bonded Co/h-BN Contacts to Ultrathin Black Phosphorus Devices

Cited by in corpus (10)

• High-Specific-Power Flexible Transition Metal Dichalcogenide Solar Cells
• Uncovering the Effects of Metal Contacts on Monolayer MoS2
• Wavelength-Controlled Photocurrent Polarity Switching in BP-MoS${}_2$ Heterostructure
• Strong Coupling of Coherent Phonons to Excitons in Semiconducting Monolayer MoTe${}_2$
• Visualizing the microscopic origins of topology in twisted molybdenum ditelluride
• Correlating the Electronic Structures of Metallic/Semiconductor MoTe2 Interface to its Atomic Structures
• Application-Driven Synthesis and Characterization of Hexagonal Boron Nitride on Metal and Carbon Nanotube Substrates
• A Polymeric Planarization Strategy for Versatile Multi-terminal Electrical Transport Studies on Small, Bulk Quantum Materials
• Electrical contact properties between Yb and few-layer WS${}_2$
• A back-to-back diode model applied to MoS2 van der Waals Schottky diodes