High-Performance WSe₂ Phototransistors with 2D/2D Ohmic Contacts

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Two-dimensional (2D) materials offer unique electronic and optical properties.
• Tungsten diselenide (WSe₂) is a promising 2D semiconductor for optoelectronic applications.
• Schottky barriers at contacts can limit the performance of 2D material-based devices.

Purpose of the Study:

• To engineer high-performance WSe₂ phototransistors.
• To investigate the impact of 2D contacts on device performance.
• To understand the mechanisms behind enhanced photoresponsivity and fast response times.

Main Methods:

• Fabrication of WSe₂ phototransistors utilizing degenerately p-doped WSe₂ for source/drain contacts.
• Characterization of device performance, including photoresponsivity, external quantum efficiency, response time, and specific detectivity.
• Analysis of the electrical transport properties and photocurrent generation mechanisms.

Main Results:

• Achieved concurrent high photoresponsivity (∼600 mA/W) and external quantum efficiency (up to 100%).
• Demonstrated fast response times (< 8 μs) and high specific detectivity (∼10¹³ Jones) in vacuum.
• Attributed performance gains to the absence of Schottky barriers between doped and undoped WSe₂.

Conclusions:

• 2D contacts formed by degenerately doped WSe₂ eliminate Schottky barriers, enhancing phototransistor performance.
• This strategy simultaneously improves electrical transport and photocurrent generation.
• Paves the way for advanced 2D optoelectronic device architectures.