Recessed-Channel WSe₂ Field-Effect Transistor via Self-Terminated Doping and Layer-by-Layer Etching

Area of Science:

• Semiconductor Physics
• Materials Science
• Nanotechnology

Background:

• Selective ion implantation is effective for Si and III-V semiconductors but not ultrathin van der Waals materials.
• Achieving low contact resistance and high on/off ratios is critical for advanced FETs.

Purpose of the Study:

• To develop a self-aligned fabrication process for ultrathin tungsten diselenide (WSe2) field-effect transistors (FETs).
• To enable low contact resistance and high on/off current ratios in WSe2 FETs.

Main Methods:

• A self-aligned process combining self-terminated p-doping and layer-by-layer chemical etching.
• Damage-free thinning of WSe2 channels to approximately 1.4 nm.
• Utilizing ultraviolet-ozone treatment to form a self-terminated tungsten oxide (WOx) layer for p-doping.

Main Results:

• Achieved low contact resistance (0.9-6.1 kΩ·μm) and a high on/off current ratio (>10^8).
• Demonstrated a field-effect mobility of approximately 190 cm²/V·s.
• The process is reproducible and does not require post-annealing.

Conclusions:

• The developed method facilitates the fabrication of high-performance recessed-channel WSe2 FETs.
• This approach is applicable to advanced two-dimensional semiconductor devices and post-silicon complementary metal-oxide semiconductor technologies.