Polarity-Tunable Photocurrent through Band Alignment Engineering in a High-Speed WSe₂/SnSe₂ Diode with Large Negative...

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Layered van der Waals (vdW) materials offer excellent light-matter interaction and tunable bandgaps for optoelectronics.
• Achieving high photoresponsivity with fast switching speeds is essential for 2D optoelectronics in optical communication.

Purpose of the Study:

• To explore a WSe2/SnSe2 type-III heterostructure for high-performance photodetection.
• To leverage tunneling current and band shifts for enhanced photoresponsivity and speed.
• To achieve controllable switching of photocurrent polarity.

Main Methods:

• Fabrication of WSe2/SnSe2 heterostructures with a type-III configuration.
• Investigation of light-induced heterointerface band shifts.
• Electrical characterization of photocurrent response under varying bias conditions.
• Density functional theory (DFT) calculations for band structure analysis.

Main Results:

• Demonstrated high negative photoresponsivity (2 × 10^4 A/W) due to steep tunneling current changes and band shifts.
• Achieved fast response times of approximately 1 μs, enabling high-speed operation.
• Showcased controllable switching of photocurrent from positive to negative values (∼10^4× enhancement).
• DFT calculations confirmed electric-field-dependent interlayer band structure modifications.

Conclusions:

• The WSe2/SnSe2 type-III heterostructure overcomes limitations of conventional pn junctions for 2D optoelectronics.
• The device's high negative responsivity, fast speed, and tunable photocurrent enable next-generation multifunctional optoelectronic devices.
• This work paves the way for advanced photodetection and optical communication applications.