PbS QD-Coated Si Micro-Hole Array/Graphene vdW Schottky Near-Infrared Photodiode for PPG Heart Rate Measurement

Area of Science:

• Materials Science
• Optoelectronics
• Biomedical Engineering

Background:

• Near-infrared (NIR) photodetectors are crucial for noninvasive medical applications.
• Self-filtered NIR photodetectors offer wavelength discrimination, enhancing their utility.
• Existing silicon/graphene photodetectors require further optimization for performance.

Purpose of the Study:

• To design and fabricate a novel self-filtered NIR photodiode.
• To enhance photodetector performance using a silicon micro-hole array and graphene van der Waals heterostructure.
• To investigate the potential of PbS quantum dot coating for improved NIR detection.

Main Methods:

• Fabrication of a silicon micro-hole array/graphene van der Waals Schottky photodiode.
• Application of a PbS quantum dot coating to the photodiode structure.
• Characterization of the photodiode's responsivity, response speed, and self-filtered NIR response.
• Integration into a photoplethysmography system for heart rate monitoring.

Main Results:

• The fabricated Si MHA/Gr vdW photodiode with PbS QD coating demonstrated a self-filtered NIR response.
• Achieved a high responsivity of 0.7 A/W at -1 V and a fast response speed of 61 μs.
• Observed enhanced performance attributed to light trapping by the Si MHA and PbS QD coating.
• Successfully monitored heart rate in real-time using photoplethysmography with accurate results.

Conclusions:

• The developed Si MHA/Gr vdW photodiode with PbS QD coating exhibits excellent self-filtered NIR detection capabilities.
• The device's high responsivity and fast response speed surpass previous Si/Gr Schottky photodiodes.
• The photodiode shows significant potential for practical biomedical applications, including noninvasive heart rate monitoring.