Self-powered ultraviolet photodetector enabled by a quasi-n-p-n heterostructure of SnO2 colloidal quantum dots, p-GaN, and a two-dimensional electron gas at the AlGaN/GaN interface

Ultraviolet photodetectors (UV-PDs) are essential for a wide range of applications, yet their practical use is often limited by challenges such as low responsivity, high noise, and significant dark current, particularly in self-powered configurations. In this work, we present a self-powered UV photodetector based on SnO₂ colloidal quantum dots (CQDs) integrated with a p-GaN/AlGaN/GaN heterostructure. The device utilizes the built-in electric field at the SnO₂/p-GaN interface to achieve self-powered operation and incorporates a quasi-n-p-n heterostructure formed between the SnO₂ CQDs (n-type), p-GaN (p-type), and the 2DEG (n-type) at the AlGaN/GaN interface to enhance carrier separation and transport, while minimizing dark current. The device demonstrates an ultra-low dark current of 370 fA in self-powered mode. At 255 nm and 340 nm, it achieves responsivities of 90.3 mA W⁻¹ and 321.1 mA W⁻¹, respectively, with specific detectivities of 4.32 × 10¹² and 1.58 × 10¹³ Jones. The photodetector exhibits strong broadband UV sensitivity spanning from 250 nm to 370 nm and sharp selectivity, with R₂₅₅/R₄₀₀ and R₃₄₀/R₄₀₀ ratios exceeding 10⁴. This work highlights the potential of SnO₂/p-GaN/AlGaN/GaN-based self-powered UV photodetectors for advanced applications in UV communication, environmental monitoring, and defense systems, offering a platform for efficient and portable photonic devices.