Reversible photo-induced doping in WSe₂ field effect transistors

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Two-dimensional (2D) materials like tungsten diselenide (WSe2) are promising for next-generation electronics.
• Controlling charge doping in 2D transistors is crucial for device performance and functionality.
• Defects in substrate materials can significantly influence the electronic properties of 2D materials.

Purpose of the Study:

• To investigate the photo-induced doping effect in WSe2 field-effect transistors (FETs) on hexagonal boron nitride (h-BN) substrates.
• To identify the underlying mechanisms responsible for the observed doping effect.
• To explore the stability and performance of photo-doped WSe2 transistors.

Main Methods:

• Fabrication of WSe2 FETs on h-BN substrates.
• Low-intensity visible light illumination experiments.
• Electrical characterization of WSe2 FETs before and after illumination.
• Analysis of defect-related contributions to doping.

Main Results:

• A reversible photo-induced doping effect was observed in WSe2 FETs under low-intensity visible light (∼10 nW μm-2).
• The doping effect is primarily attributed to specific defect types present in the h-BN substrates.
• Photo-doped WSe2 transistors demonstrated stability for over a week in the dark, maintaining a high on/off ratio (10^8) and carrier mobility.
• The absence of additional impurities prevented increased Coulombic scattering, preserving high device performance.

Conclusions:

• Photo-induced doping provides an accessible strategy for controlling charge doping levels in 2D transistors.
• This method enables a writing/erasing process for tuning the electronic properties of 2D devices.
• The study offers insights into defect states and interfacial phenomena in 2D material systems.
• The findings pave the way for novel applications in tunable 2D electronic devices.