Explanation:

Depletion region is a region that is depleted of majority charge carriers (electrons or holes) in a p-n junction diode. It is formed due to diffusion of charge carriers from one region to the other, resulting in the formation of a potential barrier. The width of the depletion region depends on various factors such as doping concentration, applied voltage, temperature, etc.

Effect of Reverse Biasing on Depletion Region Width:

When a p-n junction diode is reverse biased, the potential barrier at the junction is increased. This causes the depletion region to widen as the majority charge carriers are pushed away from the junction by the increased potential barrier. The width of the depletion region increases with an increase in the reverse bias voltage. Therefore, option B is the correct answer.

Effect of Forward Biasing on Depletion Region Width:

When a p-n junction diode is forward biased, the potential barrier at the junction is reduced. This allows the majority charge carriers to flow across the junction, resulting in a reduction in the width of the depletion region. The width of the depletion region decreases with an increase in the forward bias voltage.

Effect of Doping Concentration on Depletion Region Width:

The width of the depletion region is inversely proportional to the doping concentration. A higher doping concentration reduces the width of the depletion region, while a lower doping concentration increases its width.

Conclusion:

Thus, the width of the depletion region in a p-n junction diode is increased by reverse biasing. This is because the potential barrier at the junction is increased, causing the majority charge carriers to be pushed away from the junction, resulting in a wider depletion region.