Improved contacts to p-type MoS₂ transistors by charge-transfer doping and contact engineering

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Monolayer molybdenum disulfide (ML MoS₂) typically exhibits n-type semiconductor behavior due to intrinsic band structure and Fermi level pinning.
• Controlling the conductivity type is crucial for developing advanced electronic devices.

Purpose of the Study:

• To investigate the combined effects of molecular doping and contact engineering on the transport and contact properties of ML MoS₂.
• To achieve significant p-type (hole-transport) behavior in ML MoS₂ devices.

Main Methods:

• Fabrication of ML MoS₂ field-effect transistors.
• Application of chemical doping treatments.
• Engineering of electrical contacts using high work function (Palladium) and low work function (Titanium) metals.

Main Results:

• Significant p-type behavior was achieved in chemically doped MoS₂ devices with Palladium contacts.
• ML MoS₂ transistors with Pd contacts demonstrated effective hole mobilities of (2.3 ± 0.7) cm² V^-1 S^-1 and an on/off ratio exceeding 10⁶.
• Low contact resistances ((482 ± 40) kΩ μm) and a Schottky barrier height of ≈156 meV were obtained for p-type MoS₂ transistors.
• A MoS₂ inverter was successfully fabricated using pristine (n-type) and p-doped ML MoS₂.

Conclusions:

• Combined molecular doping and Palladium contact engineering is an effective strategy to achieve p-type behavior in ML MoS₂.
• This approach facilitates the development of high-efficiency 2D-based semiconductor devices, including complementary circuits.
• The study presents a simple and effective route for contact engineering in 2D materials.