Question

What is the effect of forward and reverse biasing on depletion layer?

Answer 1

1. A p-n junction of a diode is the interface between a p-type and an n-type semiconductor. A p-type semiconductor has an extra number of holes whereas an n-type semiconductor contains an extra number of electrons.
2. At the junction, the electrons from the n-type get attracted to the positive holes from the p-type side. Some of the electrons combine with the holes, thereby making the p-side negatively charged and the n-side positively charged near the junction. This creates an electric field within the semiconductor.
3. The combination of electrons and holes stops once the generated electric field at the junction opposes the diffusion of electrons from the n-side. This charged region at the junction is known as the depletion layer.
4. If a higher potential and a lower potential is applied on the two sides of a p-n junction, the diode is said to biased

Forward biasing:

1. If a positive (higher) potential is connected to the p-type and a negative (lower) potential is connected to the n-type, the diode is said to be forward-biased.
2. In this scenario, the applied electric field causes holes from the p-side to combine with the negative charge at the junction. Similarly, the electrons from the n-side are pushed towards the junction and combine with the positive holes at the junction.
3. The applied electric field, in this case, is in the opposite direction as that of the electric field of the depletion layer. This causes the depletion layer to shrink.

Reverse biasing:

1. If a positive (higher) potential is connected to the n-type and a negative (lower) potential is connected to the p-type, the diode is said to be reverse biased.
2. In this scenario, the applied electric field causes holes from the p-side to to move away from the junction and similarly, the electrons from the n-side are moved away from the junction.
3. The applied electric field, in this case, is in the same direction as that of the electric field of the depletion layer. This causes the depletion layer to widen.