p-n Junction Diode :-
A p-n junction is a boundary or interface between two types of semiconductor materials, p- type and n- type inside a single crystal of semiconductor. It is the basic building block of semiconductor device like p-n junction diode.
- p-n junction diode with metallic contracts provided at the ends for the application of an external voltage. It is two terminal device.
- The direction of arrow indicates the conversational direction of current ( When the diode under forward bias ).
p-n Junction Diode under forward bias :-
When an external voltage V is applied across a semiconductor diode such that p – side is connected to the positive terminal of the battery and n – side to the negative terminal, it is said to be forward biased.
The applied voltage mostly drops across the depletion region and the voltage drop across the p – side and n – side of the junction is negligible. The direction of the applied voltage V is opposite to the built in potential V₀ . As a result, the depletion layer width decreases and the barrier height is reduced.
- In the forward biasing of p-n junction, p-side of junction is connected to higher potential and n – inside of junction diode is connected to lower potential.
p-n Junction Diode under reverse bias :-
When an external voltage V is applied across the diode such that n-side is positive and p-side is negative, it is said to be reverse biased.
- The applied voltage mostly drops across the deplection reason. The direction of applied voltage is same as the direction of barrier potential. As a result, the barrier height increases and the deplection reason widens due to the change in electric field.
- The diode reverse current is not very much dependent on the applied voltage. Even a small voltage is sufficient to sweep the minority carriers from one side to another of the junction.
- The current under reverse bias is essentially voltage dependent up to a critical reverse bias voltage, known as breakdown voltage.
Note :- The p-n junction diode primerly allows the flow of current only in one direction (forward bias). The forward bias resistance is low as compared to the reverse bias is low as compared to the reverse bias resistance. This property is used for rectification of AC voltage.
Uses of p-n Junction Diode :-
- It is used as rectifiers in DC power supply manufacturing.
- It is also used as Zener diode in peak clippers, voltage regulators and for switching.
- It is used in detector and demodulator circuits.
- It can be used as a solar cell.
- When the diode is forward biased, it can be used in LED lighting.
- It can be used as a photodiode as the diode is sensitive to the light when the diode is reverse biased.