NiO/GaN p-n junction ultraviolet photodetector and self-powered technology

Abstract

<sec> Ultraviolet photodetector plays an important role in fire warning, missile tracking and dose detecting of ultraviolet sterilization and disinfection, which is closely related to human lives. With the development of integrated detection system, the requirements for the size and energy consumption of the detector are becoming more and more stringent. Traditional detector that requires an external power supply can no longer meet these requirements. Moreover, a traditional ultraviolet detector is mainly composed of first-generation semiconductors and second-generation semiconductors. These semiconductors have small band gaps and large cut-off wavelengths, and are more suitable for infrared detection. When used for implementing the ultraviolet detection, an additional layer is often required, which increases not only the volume but also the cost. </sec><sec> Gallium nitride (GaN), as a third-generation semiconductor, has a band gap of 3.4 eV and a corresponding absorption edge of 365 nm. It is a natural ultraviolet detection material. At the same time, the excellent physical and chemical properties make the devices prepared by GaN have high stability. In recent years, some studies have shown that the GaN-based ultraviolet photodetectors have excellent responsiveness, but each of these detectors usually requires an external bias and has a slow response speed. Here, we propose a high responsivity, fast response speed and self-powered ultraviolet photodetector based on NiO/GaN p-n junction. By using the magnetron sputtering, a layer of 70 nm thick p-NiO film is deposited on a high-quality n-GaN film that has been grown on a sapphire substrate by the metal-organic chemical vapor deposition. The fabricated p-n junction shows obvious rectification characteristics at ± 0.5 V. Due to the existence of the built-in electric field, the device can work without externally applied bias. Under zero bias, the detector shows a responsivity of 272.3 mA/W for 365 nm ultraviolet light while the intensity is 50 μW/cm², and has a detectivity as high as 2.83 × 10¹⁴ Jones. This indicates that the detector has a high sensitivity even for very weak light. Owing to the good crystallinity of the film, the dark current is as low as 10^–10 A, the switching ratio is > 10³, and the response speed reaches 31 ms. These excellent properties show the broad application prospects of the devices based on NiO/GaN p-n junctions in the field of self-powered ultraviolet detection, and thus providing new ideas for the future development of intelligent integration. </sec>