Vacuum ultraviolet (VUV) detectors have a wide range of applications in fields such as gas analysis and material surface research. However, photomultiplier tubes, which are currently the predominant VUV detectors, have several disad-vantages, including large size and high power consumption. Therefore, there is an urgent need to develop vacuum ultra-violet detectors that offer advantages such as miniaturization, low power consump-tion, and fliters-free. This study em-ployed metal-organic chemical vapor deposition (MOCVD) technology to establish an ohmic contact between the n-type AlGaN layer and the metal, thereby addressing the challenges associated with n-type doping in AlN. Ulti-mately, an AlN-based vacuum ultraviolet detector was fabricated on a sapphire substrate. We compared the performance of two de-vices with different photosensitive surface areas. Experimental results indicate that devices exhibit supe-rior VUV detec-tion performance, achieving a higher rejection rate of 6.12 × 103, a low dark current of 7 × 10?12 A, a peak responsivity of 91.8 mA/W, and a detection rate of 2.29 × 1012 cm·Hz1/2·W?1. Such VUV detectors with high rejection ratio, are ex-pecting to support VUV dynamic imaging and single photon detection in the future.