High-Speed, UV-NIR Dual-Band Photodetection via a 2H-MoSe₂/Si/1T-WS₂ Bipolar Heterojunction

Area of Science:

• Materials Science
• Optoelectronics
• Nanotechnology

Background:

• Dual-band photodetection is crucial for various applications, including optical communication, environmental monitoring, and biomedical imaging.
• Current dual-band systems often require optical filters, increasing complexity and cost.
• Transition metal dichalcogenides (TMDs) and silicon (Si) offer promising properties for optoelectronic devices.

Purpose of the Study:

• To demonstrate a filter-free, high-speed ultraviolet (UV) and near-infrared (NIR) dual-band photodetector.
• To investigate the performance of a bipolar heterojunction (BHJ) based on 2H-MoSe₂/Si/1T-WS₂ for dual-band photodetection.
• To evaluate the device's potential for multispectral imaging applications.

Main Methods:

• Fabrication of a bipolar heterojunction (BHJ) device using 2H-MoSe₂, Si, and 1T-WS₂.
• Characterization of the device's photodetection performance under UV (365 nm) and NIR (1064 nm) illumination.
• Evaluation of response time, bandwidth, and responsivity at a bias voltage of -2 V.
• Comparative analysis with broadband silicon photodiodes for single-pixel imaging.

Main Results:

• The optimized BHJ device achieved high responsivities of 0.7 A/W at 365 nm and 0.8 A/W at 1064 nm.
• The device exhibited a fast response time of 1.28 μs and a -3 dB bandwidth of 70 kHz.
• High-quality NIR single-pixel imaging was demonstrated, reconstructing 128 × 128 pixel images under ambient lighting.

Conclusions:

• The 2H-MoSe₂/Si/1T-WS₂ BHJ structure enables efficient, filter-free UV-NIR dual-band photodetection.
• The device demonstrates high speed and responsivity, suitable for demanding optoelectronic applications.
• This work highlights the potential of TMD-Si heterojunctions for advanced multispectral sensing and imaging systems.