Dielectric‐Free MoS 2 /VO 2 Junction Field‐Effect Transistor with Sensitive and Ultrafast Photoresponse for Light Encrypted Communication

The rise of the Internet of Things and mobile devices has created a pressing demand for advanced on‐chip photodetection platforms. Two‐dimensional materials have emerged as promising photodetector candidates owing to their exceptional optoelectronic properties. However, simultaneously achieving high responsivity, low noise, and quick photoresponse remains challenging for 2D material phototransistors. This study introduces a hybrid MoS 2 /VO 2 junction field‐effect transistor (JFET) designed to address this sensitivity‐speed tradeoff. By leveraging the van der Waals (vdW) interface and adjustable depletion region via the VO 2 gate, the JFET achieves a minimal subthreshold swing (80 mVdec −1 ) and little gate hysteresis (10 mV). Furthermore, the promoted carrier transport enables a sensitive photoresponse (responsivity: 10 3 AW −1 , specific detectivity: 10 12 Jones) and fast response speed (rise/decay time: 8/10 µs). The device exhibits self‐powered photodetection at elevated temperature, a rare occurrence for phototransistors with ohmic contact, attributed to enhanced built‐in electric field at asymmetric vdW heterojunction. The JFET's effective gate controllability and sensitive photoresponse make it suitable as a low‐power light encoder for encrypted communication. This work provides the foundation for integrated optoelectronic devices based on 2D materials and heterostructures.