With the development of chip to high-density integration, the requirement of lithography precision is higher and higher. In this process, controlling the power of the lithography exposure light source is very important to improve the quality of the chip. However, most detectors are unable to conduct light detection in liquid environments, especially in the aspects of real-time detection and calibration of light power in immersion deep ultraviolet lithography. In this paper, the AlN film epitaxial on n-SiC substrate by MOCVD is used as the photoelectrode, based on which an immersion detector with a quick response to 193 nm vacuum ultraviolet (VUV) light is fabricated. Impressively, under 0 V bias, the detector achieves a high responsiveness (130 mA/W) and an EQE up to 83.7% under an excitation with lower light power (45 nW), illustrating its ability to perform highly efficient detection of light signals and underwater imaging in weak-light environment. In addition, the detector also has the shortest detection wavelength when compared with the immersion photodetectors reported so far. At the same time, the simulated immersion lithography monitoring experiment shows that the detector has good real-time monitoring ability. In a word, this work provides a novel method for detecting underwater light power and can work as reference for realizing the real-time monitoring of immersive lithography light sources in future applications. Display omitted •An immersion detector with rapid response to 193 nm VUV light was prepared using AlN/n-SiC substrate as the photoelectrode.•Under 0 V bias and 193 nm laser excitation, the detector achieves a high responsiveness (130 mA/W) and an EQE up to 83.7%.•For the first time, the real-time monitoring experiment of the light power in simulated Immersion lithography is completed.