SOLUTION

The leakage current across a PN Junction is due to minority carriers.

Detailed Explanation

When a PN-junction is reverse biased the holes in the P-region are attracted towards the negative terminal of the applied voltage source, whereas the electrons in the N-region are attracted to the positive terminal of the voltage source. Thus the majority of carriers are drawn away from the junction. This widens the depletion layer and increases the barrier potential.

⇒ The barrier potential helps the minority carriers in crossing the junction. As soon as a minority carrier is generated, it is swept (i.e., drifted) across the junction because of the barrier potential.

⇒ Hence a small amount of current (called reverse saturation current or leakage current or current due to minority charge carriers) does flow through the reverse-biased PN junction.

⇒ The amount of this current depends upon the generation of minority carriers diffusing across the junction.

⇒ It may be noted that the generation of minority carriers depends upon the temperature and is independent of the applied reverse voltage.

⇒  Therefore the current due to the flow of minority carriers remains the same whether the applied voltage is increased or decreased.

⇒ Because of this reason, the current is known as reverse saturation current.