Gate tunable WSe2-BP van der Waals heterojunction devices

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Two-dimensional (2D) semiconductor heterostructures offer tunable electronic properties via electrostatic gating due to weak charge screening.
• The ability to form different heterojunction types within a single device is crucial for advanced electronic and optoelectronic applications.

Purpose of the Study:

• To demonstrate a 'type-tunable' heterojunction device using WSe2 and black phosphorus (BP).
• To investigate the electrical and optoelectrical characteristics of the WSe2/BP heterojunction under electrostatic modulation.
• To understand the band alignment at the WSe2/BP interface.

Main Methods:

• Fabrication of a heterojunction device using ambipolar WSe2 and black phosphorus (BP) 2D materials.
• Application of electrostatic gating to modulate the charge carrier type and concentration.
• Electrical characterization to measure current rectification ratios.
• Optoelectrical measurements to analyze photocurrent response.

Main Results:

• The WSe2/BP heterojunction exhibited tunable behavior, switching between p-p and n-n junctions via gate modulation.
• The p-p junction displayed significant current rectification, while the n-n junction showed negligible rectification.
• Photocurrent amplitude and polarity were effectively modulated by electrostatic gating, indicating tunable band offsets.

Conclusions:

• The WSe2/BP heterojunction demonstrates 'type-tunable' characteristics, enabling versatile device design.
• The observed rectification behavior suggests a large valence band offset and a small conduction band offset at the interface.
• This work advances the understanding and design principles for 'type-tunable' van der Waals heterojunctions in electronic and optoelectronic devices.