Multi-effect coupling enhanced self-powered heterojunction ultraviolet photodetector with ultra-low detection limit

Abstract

Convenient, small-sized, and self-powered sensor units are easier to integrate, making them the future development direction of photodetectors. GaN materials with wide band gap are powerful candidates for UV detection, but most GaN based self-powered UV photodetectors have poor detection ability for the weak UV light, which limits their applications. This study reports a self-powered UV photodetector based on BaTiO₃/GaN heterojunction, which can detect ultra-weak UV light at a minimum of 0.68 nW/cm² by coupling the ferroelectric polarization, anti-reflection effect, and pyro-phototronic effect. The polarized BaTiO₃ thin film on the surface of GaN has an enhanced residual polarization field and generated anti-reflection effect, which can regulate the heterojunction band structure, suppress the dark current and minimize surface reflection of GaN. Simultaneously enhanced pyro-phototronic effect can significantly improve the response speed and responsivity of the device. The response time and recovery time of the device are as low as 8.794 ms and 5.018 ms. The maximum responsivity and detectivity are 88.206 mA/W and 7.392 × 10¹³ Jones, respectively, increased by 359% and 6065% compared to the device before polarization. Thanks to excellent material stability, the device has a sensitive and uniform response to continuously incident UV light. In addition, by simulating flame generation, it has been proven that the device has brilliant performance in flame detection and can achieve remote monitoring and fire warning functions. These results can promote the potential application of self-powered UV photodetectors based on BaTiO₃/GaN heterojunction in environmental monitoring and space communication fields.