Robust Light Detection from Ultraviolet to Near-Infrared with ZnGa₂O₄/p-Si Heterojunction Photodiode and Its Application for Optoelectronic Physically Unclonable Functions

The Si-based self-powered broadband photodiode (SSBP) is prized for its ability to swiftly detect light across a wide spectrum without requiring an external voltage. However, boosting its efficiency remains challenging due to its high refractive index and limited UV light penetration. A combination of Si with ZnGa₂O₄, an ultra-wide-bandgap spinel material, can bring new opportunities to address these shortcomings of SSBP. In this study, a ZnGa₂O₄/p-Si heterojunction photodiode is presented, which is capable of detecting UV to near-infrared light autonomously. Operating without bias, this device exhibits excellent rectification and detects wavelengths from 265 to 1000 nm, achieving impressive performance metrics such as a photo-to-dark current ratio of 5.8 × 10⁴, response speed of less than 3 ms, responsivity of 117 mA W⁻¹, and specific detectivity of 5.5 × 10¹² Jones while the photodiode demonstrates exceptional stability and durability under harsh conditions. The versatility of this device is demonstrated by applying it to the optical imaging sensors and physically unclonable security devices. This study provides new inspirations for the development of the energy-efficient and emerging optical sensing technologies.