What is P-N Junction Diode ? Discuss its working.

          P-N JUNCTION DIODE


What is P-N Junction Diode?

It is a two terminal device consisting of p-n juction formed either in Ge or Si crystal. The p and n-type regions are referred as anode and cathode respectively.p-n juction arrow head indicates the conventional direction of current flow when forward biased.p-n juction It is in the same direction in which the hole flow taken place.



Working : 

A semiconductor diode or p-n junction diode is a one way device offering low resistance when forward biased and behaving almost as a insulator when reverse biased. Hence, such diodes are mostly used as rectifier i.e., for converting alternating current into direct current.

Properties of p-n Junction. : 

The p-n junction possesses some properties which have useful applications in modern electronics are as follows :

  1. It is relatively conductive.
  2. It forms depletion junction which is useful in control of flow of charge carriers.
  3. Due to this non-conducting depletion layer , p-n junctions are commonly used as diodes.
  4. It makes flow of electricity in one direction only.


Potential Barrier :

 A potential barrier is a junction barrier setup against further movement of charge carriers after the process of diffusion. When two pieces of p-type and n-type material are joined together.As p-type material has a high concentration of holes and n-type material has high concentration of free electrons and hence there is a tendency of holes to diffuse over to n-side and electrons to p-side. This process is known as diffusion.
                                         When a sufficient number of donor and acceptor ions is uncovered then further diffusion is prevented. It is because now positive charge on n-side repels holes to cross from p-type to n-type and negative charge on p-side repels free electrons to enter form n-type to p-type. Thus,a barrier is formed which stops further movement of charges carriers.
                                          The barriers can be increased or decreased by applying and external voltage.It is clear from figure that a potential barrier VB is setup which gives rise to electric field. This field prevents the prevents the respective majority carriers from crossing the barrier region. The potential barrier is of the order of 0.1 to 0.3 volt. 


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