When a PN junction is forward biased

Concept:

• When a p-type semiconductor crystal is brought into close contact with an n-type semiconductor crystal, the resulting arrangement is called p-n junction diode.

Explanation:

Forward Bias –

• When the negative terminal of the battery is connected to N – side and the positive terminal to P –side, then the connection is called forward bias. 
• In forward biasing, the applied voltage V of the battery mostly drops across the depletion region and the voltage drops across the p-side and n-side of the p-n junction is negligibly small.
• It is because the resistance of the depletion region is very high as it has no free charge carriers.
• In forward biasing the forward voltage opposes the potential barrier V_b. As a result of it, the potential barrier height is reduced and the width of the depletion layer decreases.
• As forward voltage is increased, at a particular value the depletion region becomes very much narrow such that a large number of majority charge carriers can cross the junction.

Reversed Bias –