The photodetector realizes the role of converting light into electricity in the optical communication system. This is mainly based on the photovoltaic effect of semiconductor materials. The so-called photovoltaic effect refers to the uneven semiconductor or semiconductor and metal bonding between different parts of the light. The phenomenon of potential difference. With the continuous advancement of science and technology, there is now a newer technology: high speed photodetector.

The photoconductivity effect refers to the phenomenon that electrons absorb the 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 based It is a kind of physics that the electrons in the valence band of the photoelectric material will be excited to the conduction band to increase the conductivity of the photoconductor, which means that the conductivity of the irradiated material changes due to radiation. The phenomenon, photons act on the photoconductive material, forming intrinsic absorption or impurity absorption, and generating additional photo-generated carriers, which changes the conductivity of the semiconductor and produces a photoconductive effect.