Extension Doping with Low-Resistance Contacts for P-Type Monolayer WSe₂ Field-Effect Transistors.

Area of Science:

• Materials Science
• Nanotechnology
• Semiconductor Physics

Background:

• Source/Drain extension doping is critical for minimizing resistance in field-effect transistors (FETs) for advanced complementary metal-oxide-semiconductor (CMOS) technology.
• Two-dimensional (2D) semiconductors like molybdenum disulfide (MoS2) and tungsten diselenide (WSe2) are promising for next-generation CMOS devices.
• A significant challenge lies in achieving effective extension doping for 2D monolayer FETs without causing material degradation.

Purpose of the Study:

• To demonstrate a method for extension doping of monolayer WSe2 p-FETs.
• To achieve low-resistance contacts and high performance in 2D FETs.
• To develop strategies for damage-free, nanometer-scale selective-area doping in 2D materials.

Main Methods:

• Utilized self-limiting oxidation to convert bilayer WSe2 into a WOxSey/WSe2 hetero-bilayer.
• Employed damage-free nanolithography to define an undoped nano-channel.
• Inserted an amorphous WOxSey interlayer beneath the contacts to reduce contact resistance.

Main Results:

• Achieved record-low contact resistances for monolayer WSe2 (1.2±0.3 kΩ μm at 10^13 cm^-2).
• Demonstrated a WOxSey-doped extension with a low sheet resistance of 10±1 kΩ □^-1.
• Monolayer WSe2 p-FETs with sub-50 nm channels exhibited a maximum drain current of 154 μA μm^-1 and an on/off ratio of 10^7-10^8.

Conclusions:

• The developed method enables effective extension doping and low-resistance contacts for monolayer WSe2 p-FETs.
• The approach preserves the high on-current while significantly improving the on/off ratio.
• This work provides a viable strategy for nanometer-scale selective doping in 2D FETs and other 2D electronic architectures.