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. Photodetectors based on SnS2/ReSe2 heterostructures are fabricated and their optoelectronic performance and working mechanisms are studied. Leveraging the tunneling mechanism of the devices, they maintain high detection rates and rapid response speeds across a broad spectral range from NUV to NIR. The devices have great potential in high‐resolution single‐pixel imaging and ASCII communication.