Fermi-level depinning achieved by high-work-function Au_1-xSe_x alloy contacts for high-performance p-type WSe₂...

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Fermi-level pinning (FLP) in two-dimensional (2D) transition metal dichalcogenides (TMDs) hinders p-type device performance.
• High-work-function metal deposition causes significant damage and exacerbates FLP in 2D materials.

Purpose of the Study:

• To develop a novel contact strategy for achieving Fermi-level depinning in monolayer WSe2 p-type transistors.
• To mitigate defect-induced gap states (DIGS) and metal-induced gap states (MIGS) in 2D materials.

Main Methods:

• Utilized molecular beam epitaxy (MBE) to create Au1-xSex alloy contacts.
• Employed a low-temperature deposition process involving pre-deposition of selenium (Se) followed by gold (Au) deposition.
• Formed a van der Waals (vdW) interface between the alloy contact and monolayer WSe2.

Main Results:

• Achieved Fermi-level depinning in monolayer WSe2 p-type transistors using Au1-xSex alloy contacts.
• Demonstrated quasi-ohmic contact behavior with a contact resistance of 492 Ω·µm.
• Obtained high device performance with an on-current of 385 µA/µm and an on/off ratio > 10^8.

Conclusions:

• The Au1-xSex alloy contact strategy effectively reduces Schottky barrier height and improves p-type 2D device performance.
• This method offers a scalable solution for fabricating high-performance p-type 2D electronic devices.
• The developed contact strategy mitigates DIGS and MIGS, enabling superior electronic properties.