Light absorption improvement and mechanism analysis of single photon avalanche diode with metal gratings

The single photon avalanche diode (SPAD) detector with metal nanograting structure is simulated, and light absorption mechanism in the near-infrared region is analysed. The period, thickness, dielectric layer thickness and other parameters of Ag gratings at 850 nm communication wave-length are optimized. Combined with FDTD optical simulation results, TCAD simulation was used to adjust the depth of pn junction to about 0.8 μm at the wavelength of 850 nm. The depth of depletion region and light absorption region are matched to improve the light absorption efficiency in the near-infrared region.