Self-Powered Ultraviolet Photodetector with Superhigh Photoresponsivity (3.05 A/W) Based on the GaN/Sn:Ga₂O₃ pn Junction

TLDR

Ultraviolet radiation affects human health, crop production, and building durability, yet current self‑powered UV photodetectors suffer from low photoelectric performance that limits practical use. The authors fabricated a GaN/Sn:Ga₂O₃ pn junction by depositing a Sn‑doped n‑type Ga₂O₃ thin film onto a p‑type GaN thick film to create a self‑powered UV photodetector. The device achieved a 3.05 A/W responsivity at 254 nm, a UV/visible rejection ratio of 5.9 × 10³, a detectivity of 1.69 × 10¹³ cm·Hz¹ᐟ²·W⁻¹, a dark current of 1.8 × 10⁻¹¹ A, an Iphoto/Idark ratio of ~10⁴, and an 18 ms response time, all enabled by rapid carrier separation in the junction’s high built‑in field.

Abstract

Ultraviolet (UV) radiation has a variety of impacts including the health of humans, the production of crops, and the lifetime of buildings. Based on the photovoltaic effect, self-powered UV photodetectors can measure and monitor UV radiation without any power consumption. However, the current low photoelectric performance of these detectors has hindered their practical use. In our study, a super-high-performance self-powered UV photodetector based on a GaN/Sn:Ga2O3 pn junction was generated by depositing a Sn-doped n-type Ga2O3 thin film onto a p-type GaN thick film. The responsivity at 254 nm reached up to 3.05 A/W without a power supply and had a high UV/visible rejection ratio of R254 nm/R400 nm = 5.9 × 103 and an ideal detectivity at 1.69 × 1013 cm·Hz1/2·W–1, which is well beyond the level of previous self-powered UV photodetectors. Moreover, our device also has a low dark current (1.8 × 10–11A), a high Iphoto/Idark ratio (∼104), and a fast photoresponse time of 18 ms without bias. These outstanding performance results are attributed to the rapid separation of photogenerated electron–hole pairs driven by a high built-in electric field in the interface depletion region of the GaN/Sn:Ga2O3 pn junction. Our results provide an improved and easy route to constructing high-performance self-powered UV photodetectors that can potentially replace traditional high-energy-consuming UV detection systems.