A ferroelectric relaxor polymer-enhanced p-type WSe₂ transistor

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Tungsten diselenide (WSe2) is a promising 2D material for p-type field-effect transistors (p-FETs) due to its air stability and high carrier mobility.
• However, WSe2's Fermi level near the band gap middle leads to high contact resistance and requires high operating voltages for sufficient ON/OFF ratios.

Purpose of the Study:

• To develop a stable p-doping technique for WSe2 to overcome contact resistance limitations.
• To investigate the dual role of a ferroelectric polymer as both a p-dopant and a high-k gate dielectric for WSe2 FETs.
• To explore the temperature-dependent performance of WSe2 FETs utilizing this novel doping and gating approach.

Main Methods:

• Coating WSe2 with a ferroelectric relaxor polymer, P(VDF-TrFE-CFE), for stable p-doping.
• Fabrication of WSe2 field-effect transistors (FETs) using P(VDF-TrFE-CFE) as both a dopant and a top gate dielectric.
• Low-temperature characterization of FET device performance to study carrier density and mobility variations.

Main Results:

• Achieved a dramatic enhancement in field-effect hole mobility from 27 to 170 cm² V⁻¹ s⁻¹ for six-layer WSe2 FETs.
• Demonstrated high p-type performance in bilayer WSe2 FETs with P(VDF-TrFE-CFE) as the top gate dielectric at low top gate voltages.
• Observed a significant increase in field-effect hole mobility, reaching up to 900 cm² V⁻¹ s⁻¹ at 200 K, correlating with the polymer's phase transition.

Conclusions:

• The P(VDF-TrFE-CFE) coating provides an effective and stable method for p-doping WSe2, simultaneously acting as a high-k gate dielectric.
• This combined approach significantly boosts the performance of WSe2-based p-FETs, enabling operation at lower voltages.
• The findings offer a promising strategy for realizing high-performance logic devices based on 2D semiconductors.