HgTe Quantum Dots/WSe 2 Mixed‐Dimensional van der Waals Phototransistor for GateTunable Telecom‐Band Photodetection and Dual‐Channel Encrypted Optical Communication

Short‐wave infrared (SWIR) photodetectors operating at the telecommunication bands are indispensable for optical interconnects and secure communication, yet low‐cost alternatives to epitaxial infrared semiconductors remain scarce. Herein, a 0D/2D mixed‐dimensional van der Waals phototransistor is demonstrated by integrating HgTe quantum dots (QDs) with a WSe 2 channel. Benefiting from the type‐I nested band alignment, photoelectrons are trapped within the QDs to form a negative photogate, whereas photo‐holes are injected into the p‐type WSe 2 channel, yielding a pronounced photogating gain that is further amplified under negative gate bias. The device delivers high responsivities of 2858 and 2337 A W − 1 at 1310 and 1550 nm, respectively. The peak specific detectivity derived from flicker‐noise spectra reaches 5.31 × 10 10 Jones at 1310 nm, while the shot‐noise‐limited detectivity is 4.37 × 10 12 Jones. Leveraging the synchronous visible‐to‐SWIR photoresponse, a dual‐channel encrypted optical communication scheme is further realized, in which a 635 nm key channel delivers time‐dependent permutation rules while a 1310 nm channel transmits American Standard Code for Information Interchange‐encoded data enabling real‐time decryption of “SCNU”. This work establishes a viable route toward low‐cost, gate‐tunable SWIR photodetectors and highlights the potential of 0D/2D heterojunctions for externally encoded dual‐wavelength optical signaling with software‐assisted decoding.