Fig. 1. Application of the extreme ultraviolet (EUV) photodetector in electronics manufacturing and space exploration. (a) Schematic diagram of EUV lithography system^[3]; (b) simplified schematic diagram of laser–droplet interaction in a typical industrial EUV light source module^[4]; (c) emission spectrum of Sn in EUV wavelength range^[4]; (d) optical system and mechanical design cross-section of EUV reflective components; (e) defect structures smaller than 50 nm of the EUV imaging detection^[11]; (f) height fluctuation of a mask generated by an EUV microscope in the RIM-13 tool; (g) appearance of the solar disk and the SDO spacecraft used for developing solar irradiance forecasting capabilities^[14]; (h) a comparison between the daily total energy of EUV photons with a wavelength shorter than 120 nm and the energy of solar wind particles^[14]; (i) a comparison between the wavelength coverage ranges of various extreme ultraviolet variability experiment (EVE) instruments and the solar minimum spectrum obtained by the prototype EVE instrument on April 14, 2008^[14]

Fig. 2. Research progress of the gas EUV detectors. (a) Schematic diagram of the working principle of a gas monitoring detector (GMD)^[32]; (b) detection limits of the GMD for various rare gases^[33]; (c)‒(d) pulse signals obtained by measuring xenon gas and the flight time for Xe²⁺ and Xe³⁺ ions^[34]; (e) simplified model diagram of the online photoionization spectrometer (OPIS)^[43]; (f) relative deviation between the photon flux measured by GMD and that measured by the photodiode^[35]

Fig. 3. Research progress of the EUV scintillators. (a) Photograph of ZnO crystal scintillator^[59]; (b)‒(c) time distribution of ZnO fluorescence under excitation of EUV light at 13.9 nm, with the red line representing the decay fitting function^[59]; (d) quantum efficiency of sodium salicylate in the 50‒400 nm spectral range^[74]; (e) product photograph of the sodium salicylate scintillator^[77]; (f) continuous spectrum and cross-sectional SEM image of the fluorescent nanodiamonds under 344 nm light excitation^[58]

Fig. 4. Research progress of the microchannel plate detectors. (a)‒(b) Schematic diagrams of the working principle of the microchannel plate; (c) product diagram of the microchannel plate from Hamamatsu Corporation^[101]; (d) Hamamatsu Corporation improved the detection efficiency of the microchannel plate by selecting an appropriate bias angle^[101]

Fig. 5. Research progress of the silicon-based EUV photodetectors. (a) Schematic diagram of the device structure of a silicon photodiode^[103]; (b)‒(c) quantum efficiency of silicon photodiodes with Ag and Al thin films covering the device surface for filtering^[103]; (d) spectral responsivity of boron-doped silicon photodiodes in the range of 3 to 15 nm^[106]; (e)‒(f) diagram of the AXUV device as well as its spectral responsivity in the range of 0 to 250 nm^[109]

Fig. 6. Research progress of the SiC-based EUV photodetectors. (a) Comparison of detection efficiency between SiC detector and traditional Si detector^[116]; (b) responsivity of 6H-SiC photodiode in the wavelength range of 1.5 to 400 nm^[117]; (c) detector schematic using a semi-transparent metal layer as the Schottky contact metal structure^[115]; (d) quantum efficiency of a 1×16 Pt/4H-SiC Schottky photodiode array^[121]; (e)‒(f) structure diagram of a 4H-SiC-based n-i-p junction EUV detector and its irradiance results^[122]

Fig. 7. Research progress of the AlGaN-based EUV photodetectors. (a) Schottky diode and its two-dimensional array responsivity after a selective substrate etching^[127]; (b) characteristic emission lines of He I at 58.4 nm and He II at 30.4 nm in the reverse-structure AlGaN-on-Si photodiodes^[128]; (c) decay test chart of the responsivity of AlGaN-on-Si EUV Schottky diodes compared to commercially available silicon photodiodes^[130]; (d)‒(e) structural diagrams of AlGaN-on-Si EUV imaging devices^[134]; (f) physical photograph of AlGaN focal plane arrays after packaging^[133]

Fig. 8. Research progress of the diamond-based EUV photodetectors. (a) Structural diagram of a PIM diamond-based EUV detector^[139]; (b) responsivity for PIM structure diamond-based EUV detectors with two different contact geometries in the spectral range of 20 to 80 nm ^[139]; (c) spectral response of a silicon-based AXUV detector, diamond-based PIN and MSM detectors in the range of 1 to 1000 nm^[142]; (d) flux linearity at 200 nm for diamond-based PIN 7 and MSM 8 detectors, along with their fitting functions^[144]; (e) details of the MSM and Ti/Pt/Au contact structures^[142]; (f) simulated spectral responsivity of the LYRA unit (MSM 11 detector + Al filter) between 1 and 1100 nm^[142]; (g) simulation example of LYRA radiation model for channel 1-4^[142]; (h)‒(i) absolute spectral responsivity of the Al filter-detector combination and the Zr filter-detector combination in LYRA^[142]

Fig. 9. Performance comparison of gas monitor detectors, scintillators, microchannel plates, silicon-based photodetectors and wide-bandgap semiconductor-based photodetectors for EUV photodetection