An Irradiance-Adaptable Near-Infrared Vertical Heterojunction Phototransistor

Area of Science:

• Optoelectronics
• Materials Science
• Artificial Intelligence

Background:

• Bioinspired artificial vision systems require adaptable photodetectors for real-world applications.
• Current photodetectors lack efficient, cost-effective in-sensor light adaptability.
• Near-infrared (NIR) detection is crucial for advanced robotics and machine vision.

Purpose of the Study:

• To present a novel near-infrared phototransistor with inherent light irradiance adaptability.
• To investigate the device's unique photoresponse characteristics and their underlying mechanisms.
• To demonstrate the device's ability to mimic human retinal adaptation for improved artificial perception.

Main Methods:

• Fabrication of a phototransistor using a vertically stacked graphene/lead sulfide quantum dots/graphene heterojunction.
• Characterization of the phototransistor's photoresponse speed and transfer characteristics under varying light irradiances.
• Analysis of dynamic trapping and de-trapping processes within the quantum dot film.
• Demonstration of photopic and scotopic adaptation mimicry through gate voltage control.

Main Results:

• The developed phototransistor exhibits a benign light irradiance-adaptability.
• The device shows a faster photoresponse speed compared to conventional designs.
• An abnormal transfer characteristic, induced by gate voltage-tunable Fermi levels and quantum dot trap states, was observed.
• Successful mimicry of human retinal photopic and scotopic adaptation behaviors was achieved.

Conclusions:

• The novel heterojunction phototransistor offers efficient irradiance adaptability and fast response in the near-infrared spectrum.
• The gate voltage-controlled dynamic trapping mechanism is key to mimicking biological visual adaptation.
• This work provides a promising foundation for developing advanced, environment-adaptable artificial perception devices.