| Summary: | Gallium oxide (Ga<sub>2</sub>O<sub>3</sub>) is an attractive semiconductor that is very suitable for deep ultraviolet (DUV) inspection. However, due to the existence of many types of oxygen vacancies in the amorphous Ga<sub>2</sub>O<sub>3</sub> (a-Ga<sub>2</sub>O<sub>3</sub>) film, it greatly limits the performance of the a-Ga<sub>2</sub>O<sub>3</sub>-based photodetector. Here, we perform oxygen plasma treatment on the a-Ga<sub>2</sub>O<sub>3</sub>/p-Si photodetector to reduce the concentration of oxygen vacancies in the a-Ga<sub>2</sub>O<sub>3</sub> film, so that the dark current is reduced by an order of magnitude (from 1.01 × 10<sup>−3</sup> A to 1.04 × 10<sup>−4</sup> A), and the responsivity is increased from 3.7 mA/W to 9.97 mA/W. In addition, oxygen plasma processing makes the photodetector operate well at 0 V bias. The response speed is that the rise time is 2.45 ms and the decay time is 1.83 ms, while it does not respond to the DUV illumination without oxygen plasma treating at a zero bias. These results are attributed to the fact that oxygen plasma treatment can reduce the Schottky barrier between a-Ga<sub>2</sub>O<sub>3</sub> and the electrode indium tin oxide (ITO), which promotes the separation and collection efficiency of photo-generated carriers. Therefore, this work proposes a low-cost method to improve the performance of Ga<sub>2</sub>O<sub>3</sub> film-based DUV photodetectors.
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