Exploring p-Type Contact for Monolayer WS₂ FETs Using Halogen Doping and Intermediate Layers

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Tungsten disulfide (WS₂) is a promising 2D material for next-generation electronics.
• Achieving efficient p-type contacts in WS₂ transistors remains a challenge due to Fermi-level pinning (FLP).

Purpose of the Study:

• To investigate halogen (iodine or fluorine) doping strategies for enhancing WS₂ transistor contact properties.
• To explore methods for mitigating Fermi-level pinning to achieve improved p-type behavior.

Main Methods:

• Density Functional Theory (DFT) calculations were employed to study substitutional and adsorption-based halogen doping.
• Mulliken analysis was used to understand charge flow directions.
• Intermediate layers of graphene and hexagonal boron nitride (h-BN) were introduced to address FLP.

Main Results:

• Substitutional halogen doping induced n-type behavior in WS₂.
• Adsorption-based halogen doping initially induced p-type behavior, but FLP limited its prominence.
• The WS₂-graphene-Pt interface with fluorine adsorption significantly reduced the hole Schottky barrier height.

Conclusions:

• Halogen doping is an effective strategy for tuning WS₂ transistor characteristics.
• Intermediate layers like graphene are crucial for overcoming FLP and enabling prominent p-type behavior.
• The F-adsorbed WS₂-graphene-Pt interface shows great potential for efficient WS₂-based p-type MOS transistors in CMOS applications.