Germanium infrared photodetector structure with Ge/SiO2 grating and distributed Bragg reflector for wide-angle and high response

In this research, we present numerical simulations of the electromagnetic properties of a Ge/SiO 2 grating structure with a distributed Bragg reflector at the bottom for efficient infrared absorption. We developed a single-period model to simulate an infinite periodic structure and used a Flouquet boundary condition to ensure periodic continuity. We verified the model’s accuracy by testing different mesh densities and comparing the results to theoretical calculations based on Fresnel equations. We found that using 13 meshes per wavelength resulted in an error of less than 1%. Our simulations showed that the structure has a wide incident angle range of 100 degrees at a wavelength of 1550 nm. The absorbance spectrum of the design exhibits broadband properties, covering the primary wavelengths used in optical communications. The absorbance peaks reached 85.95% and 77.08% at 1340 and 1545 nm, respectively, with a minimum absorbance of 40% around 1400 nm.