Semiconductor devices with a p-n or p–i–n structure for the detection of light.

Photodiodes are frequently used photodetectors. They are Semiconductor devices which contain a p-n junction, and often an intrinsic (undoped) Layer between the N and P layers. Devices with an intrinsic layer are called p–i–n or PIN photodiodes. Light absorbed in the Depletion Region or the intrinsic region generates electron-hole pairs most of which contribute to a photocurrent.