Photodetectors realize the function of converting light into electricity in optical communication systems, which is mainly based on the photovoltaic effect of semiconductor materials. The phenomenon of generating a potential difference. (The photoconductive effect refers to the phenomenon in which electrons absorb photon energy from the bonded state to the free state under the action of light, which causes the conductivity of the material to change. That is, when light is irradiated on the photoconductor, if the photoconductor is If the photoconductor is a semiconductor material, and the light radiation energy is strong enough, the electrons in the valence band of the photoelectric material will be excited to the conduction band, and the conductivity of the photoconductor will increase. Phenomenon, photons act on the photoconductive material, form intrinsic absorption or impurity absorption, and generate additional photogenerated carriers, thereby changing the conductivity of the semiconductor and producing the photoconductive effect.)