High-Performance WS₂ MOSFETs with Bilayer WS₂ Contacts

Area of Science:

• Materials Science
• Nanotechnology
• Semiconductor Physics

Background:

• Monolayer transition-metal dichalcogenides (TMDCs) like tungsten disulfide (WS2) are promising for scaled MOSFETs.
• Achieving stable, low-barrier contacts to monolayer TMDCs remains a significant challenge.

Purpose of the Study:

• To develop high-performance WS2-based MOSFETs by addressing contact limitations.
• To investigate the impact of bilayer WS2 (2L-WS2) in contact regions on device performance and stability.

Main Methods:

• Utilized a two-step chemical vapor deposition (CVD) process to grow 2L-WS2 in the contact regions.
• Fabricated devices with both 2L-WS2 channels and hybrid 1L-WS2 channel/2L-WS2 contact structures.
• Employed conventional metal contacts (Pd or Ni) for device fabrication.

Main Results:

• Achieved a high ON/OFF current ratio (ION/IOFF) of 10^8.
• Demonstrated a saturated drain current (ID(SAT)) of 280 μA/μm at room temperature (386 μA/μm at 78 K).
• Observed comparable performance in devices with hybrid channel thicknesses and excellent stability over 13 months.

Conclusions:

• A hybrid channel thickness approach, using 2L-WS2 in contact regions, effectively enhances WS2 MOSFET performance.
• This method overcomes contact challenges, enabling high-performance and stable 2D material-based transistors.
• The findings offer a viable strategy for advancing TMDC-based electronics.