PN Junction Diode

A semiconductor is a solid substance that has a conductivity between that of an insulator and that of most metals, either due to the addition of an impurity or because of temperature effects.

The contact surface between a p-type and a n-type semiconductor is called a PN junction. A p-n junction diode is a basic semiconductor device that controls the flow of electric current in a circuit. The "p" (positive) side contains an excess of holes, while the "n" (negative) side contains an excess of electrons. When the holes start to move towards the electrons then there is formation of the layer of electrons on the p-type and a layer of holes in the n-type side which forms a region known as depletion layer, this depletion layer is the cause of the formation potential barrier. As p is losing holes, it acquires negative charge and n is losing electrons, it acquires positive charge. If any holes wants to jump from p to n and electrons from n to p, it requires a definite potential known as potential barrier. 

Applications of PN junction diode.

• Light-emitting diode application

• Laser

• It can be also used solar cells

• It used in the detector as well as the demodulator circuit

• It is used in many circuit or diode-like, a switching diode, Zener diode, PIN photo-diode, varactor diode

• It is used as switches in digital logic design

• It can be also used p-n junction photodiodes

• It can be used as a rectifier in DC power supply

• It is also used clipping circuit

• It can be also used computers, radios, radars as wave shaping circuit