PIN photo diode

What is the PIN diode?

The PIN photodiode is a one type photodetector, it is used to convert an optical signal into an electrical signal. A photodiode in general and in this case PIN photodiode will respond to different light wavelength. It is generally the thickness of top p-type region one of the key parameters in determining the response sensitivity.

Basically, the PIN diode is a one types of a photodetector. This diode can be diagrammatical as being a PN junction. but in PIN diode intrinsic layer between the PN and layers. It converts an optical signal into an electrical signal. 

The PIN diode comprises three regions:
  1.  P - region
  2.  I - region
  3.  N-region 
In PIN diode both the P and N region are heavily doped and the region between the P and N layer where there are no majority carriers
Structure of  PIN diode
PIN diode operates in the exact same way as a normal diode. but the only difference is that depletion region, It normally exists between the P and N region in the reversed diode is larger. A region between the P and N region contains no charge carriers.

P and N region are heavily doped, P region has been doped holes and N region has been doped to contain excess electron. so the region between P and N region contain no charge carrier as any electrons or holes combine, so the depletion region has no charge carriers it acts as an insulator.

When the diode is forward biased, the carrier concentration, holes and electron is very much higher than the intrinsic level carrier concentration. 

This article also gives the various types of diode listed below: