Question

Answer in detail.

Explain the importance of the depletion region in a p-n junction diode.

Answer 1

1. The region across the p-n junction where there are no charges is called the depletion layer or the depletion region.
2. During the diffusion of charge carriers across the junction, electrons migrate from the n-side to the p-side of the junction. At the same time, holes are transported from the p-side to the n-side of the junction.
3. As a result, in the p-type region near the junction, there are negatively charged acceptor ions, and in the n-type region near the junction, there are positively charged donor ions.
4. The potential barrier thus developed, prevents the continuous flow of charges across the junction. A state of electrostatic equilibrium is thus reached across the junction.
5. Free charge carriers cannot be present in a region where there is a potential barrier. This creates the depletion region.
6. In absence of a depletion region, all the majority charge carriers from the n-region (i.e., electron) will get transferred to the p-region and will get combined with the holes present in that region. This will result in the decreased efficiency of the p-n junction.
7. Hence, the formation of a depletion layer across the junction is important to limit the number of majority carriers crossing the junction.