Enhancing Ultraviolet Responsivity of GaN p-i-n Photodetectors Through Full Depletion Thin-Layer Doping-Induced Carrier Transport Modulation

High-performance GaN-based ultraviolet (UV) photodetectors (PDs) are essential for applications in harsh-environment sensing, space-based UV monitoring, and high-speed optical communications. However, conventional GaN-based p-i-n homojunction UV photodetectors face limitations in responsivity due to significant UV absorption in the p-GaN layer. To address this issue, we propose a novel full depletion (FD) thin-layer structure incorporating a strategically placed 1-nm n-type interlayer at the p–i interface with optimized doping to enhance carrier separation and collection. Results reveal a 27.3% increase in peak responsivity, reaching 0.163 A/W at 360 nm, compared to 0.128 A/W in conventional devices. In addition, the new-structured photodetector exhibits a specific detectivity (D*) of 2.88×1013 Jones, and a low response time of approximately 37 ns. The results of experiments and simulations are highly consistent, verifying the accuracy of the proposed model. Notably, the proposed design maintains excellent electrical performance, with dark current levels comparable to those of traditional architectures, thereby ensuring device stability. The FD-thin doped layer strategy offers a straightforward yet effective route to significantly improve the responsivity of GaN-based UV photodetectors without introducing fabrication complexity or the need for heterojunction integration. This architecture presents a promising pathway toward high-efficiency UV photodetection systems for next-generation applications.