Ultimate Limit in Optoelectronic Performances of Monolayer WSe₂ Sloping-Channel Transistors

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Two-dimensional (2D) semiconductors offer advantages for future electronics due to their atomic thinness.
• Short channel effects pose challenges for scaling down traditional semiconductor devices.
• Monolayer WSe2 is a promising 2D material for high-performance electronic and optoelectronic applications.

Purpose of the Study:

• To investigate the ultimate optoelectronic performance limits of monolayer WSe2 field-effect transistors (FETs).
• To explore the impact of reduced channel length, down to 6 nm, on device performance.
• To demonstrate quasi-ballistic transport and high saturation velocity in WSe2 FETs.

Main Methods:

• Fabrication of atomically thin monolayer WSe2 FETs with a precisely engineered sloping channel.
• Utilizing a scalable micro/nanofabrication technique compatible with industry standards.
• Characterization of device performance, including saturation current, transport properties, and photoresponse.

Main Results:

• Achieved a record high saturation current of 1.3 mA/μm at room temperature, exceeding previous monolayer 2D semiconductor transistors.
• Demonstrated quasi-ballistic transport for the first time in WSe2 FETs, with a saturation velocity of 4.2 × 10^6 cm/s.
• Sloping-channel devices showed enhanced photoresponse speed, higher detectivity, and polarization resolution compared to planar devices.

Conclusions:

• Monolayer WSe2 FETs with optimized sloping channels push the boundaries of optoelectronic performance for 2D materials.
• The observed quasi-ballistic transport and high saturation velocity make WSe2 suitable for ultra-sensitive photodetectors.
• Further scaling and device engineering, including channel length reduction, can significantly improve photoresponse speed and functionality.