Performance of field-effect transistors based on Nb(x)W(1-x)S2 monolayers

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Schottky barriers in transition metal dichalcogenide (TMD) field-effect transistors (FETs) significantly impair device performance.
• Tungsten disulfide (WS2) is a promising TMD semiconductor, but Schottky barriers limit its electronic applications.

Purpose of the Study:

• To reduce the Schottky barrier in WS2-based FETs.
• To investigate the effect of niobium (Nb) doping on WS2 monolayer electronic properties.
• To fabricate and characterize p-FETs using Nb-doped WS2 (Nb(x)W(1-x)S2) as the active channel.

Main Methods:

• Fabrication of p-FETs utilizing Nb-doped WS2 monolayers.
• Electrical characterization of Nb(x)W(1-x)S2 p-FETs.
• Analysis of Schottky barrier reduction mechanisms.

Main Results:

• Monolayer Nb0.15W0.85S2 p-FETs demonstrated a high drain current (330 μA μm⁻¹), an excellent ON/OFF ratio (10⁷), and high hole mobility (∼146 cm² V⁻¹ s⁻¹).
• Nb doping successfully eliminated ambipolar behavior and significantly reduced the Schottky barrier.
• Schottky barrier reduction is attributed to W 5d, Nb 4d, and S 3p state hybridization and improved Pd metal contact metallization.

Conclusions:

• Niobium doping is a viable strategy to mitigate Schottky barriers in WS2 FETs.
• Nb-doped WS2 monolayers offer enhanced electronic properties for advanced FET applications.
• The study presents the first fabrication of p-FETs based on Nb-doped WS2 monolayers.