【Member News】Fabrication of nanocrystalline Ga₂O₃-NiO heterojunctions for large-area low-dose X-ray imaging in Sun Yat-sen University

      Recently, the research team of Professor Chen Jun from Sun Yat-sen University adopted the electron beam evaporation technology to prepare the p-n heterojunction composed of nanocrystalline Ga₂O₃ film and NiO film, which exhibits a high current rectification ratio of  6.0 × 10⁴, and investigated the X-ray detection photoconductivity gain mechanism of the Ga₂O₃ / NiO heterojunction with optimized thickness of NiO, and achieved high internal gain, high sensitivity, low detection limit, and short response time. The optimized 10 × 10 pixel detectors show uniform X-ray responses, demonstrating their promising applications in large-area X-ray imaging. The related results was published in Applied Surface Science, titled “Fabrication of nanocrystalline Ga₂O₃-NiO heterojunctions for large-area low-dose X-ray imaging”.

Abstract

      The Ga₂O₃ photoconductor has a broadband gap, a relatively large density, and a high absorption coefficient for the low-energy X-rays, which makes it possible to achieve high-sensitivity and low-energy X-ray detection. Therefore, achieving p-n heterojunction using Ga₂O₃ films is crucial for large-area, low-dose X-ray imaging. In this paper, the p-n heterojunction composed of nanocrystalline Ga₂O₃ thin films and NiO thin films was successfully prepared by electron beam evaporation,which is with a large current rectification ratio of 6.0×10⁴. This p-n heterojunction exhibits a large valence band offset up to 1.7 eV, a large conduction band offset up to 0.84 eV and a built-in potential of 0.2 eV near the interface region, , which facilitates the separation and migration of photogenerated charge carriers. An X-ray detection photoconductivity gain mechanism for Ga₂O₃ / NiO heterojunction with the optimized thickness of NiO was studied. The study achieved high internal gain（3.3×10³）, high sensitivity（3.4×10⁴ μC·G_yair^-1·cm^-2） ,low detection limit（42 μG_yair·s^-1）and short response time（2.2 ms）.The optimized 10×10-pixel detectors exhibit uniform X-ray responses, indicating that they are promising in large-area X-ray imaging applications.

Related information of the essay

Zhang, M. Chen, R. Zhan, et al. Fabrication of nanocrystalline Ga₂O₃-NiO heterojunctions for large-area low-dose X-ray imaging. Appl. Surf. Sci., 2022, 604, 154623.

DOI: 10.1016/j.apsusc.2022.154623