Ultra-weak infrared light detection based on steep-slope phototransistors

Jiadong Mei, Junzhuan Wang (), Xuetao Gan and Xiaomu Wang ()
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Jiadong Mei: Nanjing University
Junzhuan Wang: Nanjing University
Xuetao Gan: Northwestern Polytechnical University
Xiaomu Wang: Nanjing University

Nature Communications, 2025, vol. 16, issue 1, 1-8

Abstract: Abstract A photodetector’s sensitivity is conventionally quantified by specific detectivity, which balances responsivity and noise. However, we reveal that the turn-on threshold power is fundamentally governed by photo-carrier injection rather than detectivity. In conventional phototransistors/diodes, incident light cannot generate photocurrent via thermionic injection until its intensity saturates the surface potential. To overcome this limit, we design a photo-tunneling transistor with a partially dual-gated black phosphorus channel. This device breaks the injection barrier, achieving a temperature-independent subthreshold swing of ~50 mV/dec up to 250 K and reducing the threshold power by over an order of magnitude. At 80 K, it detects mid-wave infrared light with a minimum power of ~35 pW, outperforming conventional phototransistors with higher detectivity by ~30-fold. Our work redefines the sensitivity criteria for photodetectors and highlights the potential of steep-slope transistors in low-power optoelectronics, offering a pathway to ultrasensitive infrared sensing and imaging technologies.

Date: 2025
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DOI: 10.1038/s41467-025-59006-8

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