Bias Tunable SnS₂/ReSe₂ Tunneling Photodetector with High Responsivity and Fast Response Speed

2D photodetectors operating in photovoltaic mode exhibit a trade-off between response speed and photoresponsivity. This work presents a phototransistor based on SnS₂/ReSe₂ heterojunction. Under negative bias, the energy band spike at the heterojunction interface impedes the carrier drifting so that the dark current is as low as 10⁻¹³ A. The tunneling under positive bias significantly reduces the transmission time of photogenerated carriers, which enhances the responsivity and specific detectivity to 32.77 A W⁻¹ and 5.77 × 10¹¹ Jones, respectively. Under reverse bias, the enhanced built-in electric field strengthens the rapid separation of photogenerated carriers, which elevates a response speed to 10.5/24.1 µs and a 3 dB bandwidth to 54.8 kHz. The device also exhibits a broad spectral detection capability, extending from the near-ultraviolet to the near-infrared. Furthermore, this work also executed high-quality ASCII communication and high-resolution broadband single-pixel imaging, which demonstrates great promise for incorporation into future broadband optoelectronic systems.