Fig. 1. (a) Schematic diagram of InP/InGaAs SPAD; (b) Electric field distribution inside SPAD at breakdown voltage

Fig. 2. Relationship between different light wavelengths and SPAD detection efficiency from Politecnico di Milano^[3]

Fig. 3. (a) Relationship between detection efficiency and dark counts rate under different temperatures and different peak-to-peak values with 1.25 G sinusoidal gating from University of Science and Technology of China^[6]; (b) Enhanced reflection structure consisting of metal layer and three-cycle SiO₂/TiO₂ Bragg mirror made by University of Science and Technology of China^[1]

Fig. 4. Detection efficiency and dark counts rate comparison of improved and previous SPADs at 225 K from Politecnico di Milano in 2014^[4]

Fig. 5. Relationship between excess bias voltage and dark counts rate of SPAD with a diameter of 25 μm (a), 10 μm (b) at different temperatures from Politecnico di Milano in 2021^[5]

Fig. 6. Relationship between temperature and dark counts rate from Chongqing Institute of Optoelectronic Technology^[10]

Fig. 7. Detection efficiency and dark counting rate versus overbias from the Institute of Semiconductors, University of Chinese Academy of Sciences^[7]

Fig. 8. Cross-sectional view of SPAD designed by Wooiro Corporation^[13]

Fig. 9. Structure diagram of SPAD at Ecole Polytechnique Fédérale de Lausanne, SAG part is an undoped tapered InP layer^[14]

Fig. 10. Self-differential circuit at the Toshiba Research Europe Ltd^[23]

Fig. 11. Comparison of afterpulse probability with and without 10 ns dead time at temperature of 20 ℃ from the Toshiba Research Europe Ltd^[17]

Fig. 12. Distribution of dark counts rate and detection efficiency of 128×32 Geiger mode SPAD focal plane arrays made by Princeton Lightwave^[8]

Fig. 13. Target-scan of a 500 m×500 m area of Maynard, MA. by MIT^[27]

Fig. 14. Statistical distribution of dark counts rate and detection efficiency of 32×32 focal plane arrays from Hamamatsu photon^[24]

Fig. 15. Distribution of breakdown voltage and dark current of 64×64 focal plane arrays from the Institute of Semiconductors, Chinese Academy of Sciences^[7]

Fig. 16. Schematic diagram of the InAlAs/InGaAs SPAD arrays made by US Naval Laboratory^[30]

Fig. 17. Relationship between temperature and breakdown voltage of InGaAs/InAlAs SPAD at the University of Sheffield^[31]

Fig. 18. InGaAs/InAlAs SPAD made by National University of Singapore^[32]

Fig. 19. Integrated single-chip with InAlAs SPAD made by the National University of Singapore^[33]

Fig. 20. InGaAs/InAlAs SPAD made by Huazhong University of Science and Technology^[34]

Fig. 21. Material structure of InAlAsSb digital alloy avalanche photodiode from University of Virginia^[35]

Fig. 22. Layer structure of InAlAsSb digital alloy avalanche photodiode from Institute of Semiconductors, Chinese Academy of Sciences^[36]