PIN Photodiode
PIN photodiode is a kind of photo detector, it can convert optical signals into electrical signals.This technology was invented in the latest of 1950's. There are three regions in this type of diode. There is a p-region an intrinsic region and an n-region. The p-region and n-region are comparatively heavily doped than the p-region and n-region of usual p-n diodes. The width of the intrinsic region should be larger than the space charge width of a normal p-n junction. The PIN photo diode operates with an applied reverse bias voltage and when the reverse bias is applied, the space charge region must cover the intrinsic region completely. Electron hole pairs are generated in the space charge region by photon absorption. The switching speed of frequency response of photo diode is inversely proportional to the life time. The switching speed can be enhanced by a small minority carrier lifetime. For the photo detector applications where the speed of response is important, the depletion region width should be made as large as possible for small minority carrier lifetime as a result the switch speed also increases.
