Recently, the team of Associate Researcher Wei Gao from the School of Electronic Science and Engineering (School of Microelectronics), Faculty of Engineering, South China Normal University, has made a significant breakthrough in high‑performance UV–vis dual‑band photodetection and secure optical communication. The related research findings, titled *“High‑Performance Mixed‑Dimensional AlGaN/WS2 Heterojunction Photodiode Towards UV–vis Secure Communication”*, have been published online in Laser & Photonics Reviews (impact factor: 10; Wiley’s flagship journal and a top‑tier journal (Class B) of SCNU). The co‑first authors are Ph.D. candidate Shuwen Yuan (Electronic Science and Technology) and Master candidate Ziyi Ma (Integrated Circuit Engineering). Associate Researcher Wei Gao is the sole corresponding author, South China Normal University is the first affiliation, and the work was carried out in collaboration with Guangxi Normal University, University of Science and Technology of China, Zhejiang University, and Guangdong University of Technology.

   I. Industry Pain Point: Key Bottlenecks to Be Overcome in Dual‑Band Photodetection

   With the rapid development of wireless communication technologies, photodetectors have become core components in space communication, smart spectral sensing, and information security. However, existing detection techniques always face a performance dilemma that is hard to reconcile:

• Conventional single‑band detectors are prone to signal leakage, while broadband detectors suffer from severe spectral crosstalk, making them unsuitable for high‑security optical communication.

• Current UV–vis dual‑band detection schemes are generally limited by complex fabrication processes, material lattice mismatch, and high power consumption.

• Low responsivity and detectivity in the UV band, together with weak noise suppression capability, remain the core bottlenecks that restrict high‑signal‑to‑noise‑ratio UV communication and optical encryption technologies.

   Achieving a monolithically integrated UV–vis dual‑band photodetector with high sensitivity, low noise, and high spectral selectivity has become a key scientific and technical challenge in this field.

   II. Core Breakthrough: Full‑Chain Innovation from Material Structure to Physical Mechanism

   To address these industry pain points, the team realized comprehensive breakthroughs from material system, physical mechanism to device performance through the synergistic design of band engineering, interface regulation, and device structure optimization.

   1. Novel Type‑I mixed‑dimensional van der Waals heterojunction lays the foundation for high‑performance devices

   The team innovatively designed and fabricated a Type‑I mixed‑dimensional van der Waals heterojunction based on AlGaN/WS2, and optimized the device structure with a ring‑shaped drain electrode:

• The ring‑shaped surrounding electrode design greatly shortens the carrier transport path, enabling efficient charge collection within a junction area of 182.75 μm², thus overcoming the resistance bottleneck of 2D/3D heterojunctions.

• Leveraging the advantages of van der Waals integration, a high‑quality physical contact with dangling‑bond‑free and low interface state density is achieved at the heterojunction interface, effectively suppressing the dark current to the picoampere level, which lays a structural foundation for ultra‑high detectivity and ultra‑low noise.

   2. Several key performance indicators reach world‑leading levels, with comprehensive performance greatly improved

   Based on the novel device design, this photodetector achieves comprehensive performance enhancements, with core indicators ranking among the best of similar devices worldwide:

• Ultra‑high responsivity: Under 3 V bias, the responsivity reaches 164.8 A/W at 365 nm (UV) and 2.71 A/W at 405 nm (visible).

• Ultra‑high detectivity: The specific detectivities at the corresponding bands are 5.57 × 10¹³ Jones and 3.39 × 10¹¹ Jones, respectively, with a noise‑equivalent power as low as 5.7 fW/Hz¹/².

• Fast response and excellent stability: At 365 nm, fast response times of 2.03/19.8 ms are achieved. After 6 months of storage in ambient air without encapsulation, the photoresponse retains 95% of its initial value, and no obvious performance degradation is observed after 300 switching cycles.

   3. A new light‑assisted tunneling mechanism is revealed, offering a new device design paradigm

   Through systematic experimental characterization and TCAD numerical simulation, the team fully revealed the underlying physical mechanism of this heterojunction system for the first time: forward bias induces polarity reversal at the interface, driving the device from depletion mode to accumulation mode, which in turn triggers the photo‑assisted Fowler‑Nordheim tunneling effect and dynamically reshapes the tunneling barrier.

   This mechanism overcomes the inherent recombination bottleneck of conventional Type‑I heterojunctions, achieving an ultra‑high photoconductive gain. The external quantum efficiency of the device exceeds 5.61 × 10⁴ %, far beyond the unity limit of traditional devices, providing a new theoretical support and physical paradigm for the design of high‑performance heterojunction optoelectronic devices.

   III. Application Deployment: Enabling Next‑Generation Secure Optical Communication Technology

   Benefiting from the excellent UV–vis dual‑band discrimination capability and ultra‑high noise immunity, the team successfully built a wavelength‑division‑multiplexing secure optical communication system based on this device. They developed a multi‑dimensional encoding scheme based on coordinate mapping and a dual‑wavelength decryption mechanism through software‑hardware collaboration. The system achieves independent modulation of UV and visible signals, dual‑channel encrypted transmission, and real‑time demodulation. Without any external optical splitting component, the mixed signals can be accurately separated and decrypted simply by amplitude thresholding and logical‑level secondary verification, greatly increasing the information capacity and anti‑interception capability of the optical communication link. This work opens up new paths for next‑generation multi‑dimensional optical logic and secure optical communication architectures.

   This research was supported by the National Natural Science Foundation of China, the Guangzhou Science and Technology Program, and the Guangdong Provincial Key Laboratory of Chip and Integration Technology. In recent years, the team of Associate Researcher Wei Gao has focused on cutting‑edge directions such as two‑dimensional semiconductor materials and devices, wide‑bandgap semiconductor optoelectronic devices, and heterojunction integrated chips, continuously producing high‑level research achievements in logic gates, optical communication, photodetection, and neuromorphic devices.

   This achievement not only establishes a new paradigm for interface‑engineered wavelength‑selective optoelectronic devices but also lays a solid device and theoretical foundation for next‑generation wavelength‑encoded secure optical communication technology. It also fully demonstrates the strong scientific research capabilities and innovation strength of the Faculty of Engineering of SCNU in the disciplines of Electronic Science and Technology, and Integrated Circuit Science and Engineering.

   Link to the paper: https://doi.org/10.1002/lpor.71271