Introduction:
A p-n junction diode is a two-terminal semiconductor device that allows current to flow in one direction while blocking it in the opposite direction. When a diode is reverse biased, the positive terminal of the battery is connected to the n-type material, and the negative terminal is connected to the p-type material. In this configuration, the depletion region of the diode plays a crucial role.

Depletion Region:
The depletion region is a region near the junction where the majority carriers (electrons in n-type and holes in p-type) are depleted, leaving behind immobile positive and negative charges. This depletion region acts as a barrier to the flow of current.

Effect of Reverse Biasing:
When the p-n junction diode is reverse biased, the following changes occur:

1. Increased Width: The width of the depletion region increases significantly. This happens because the negative terminal of the battery repels the free electrons in the n-type material, pushing them away from the junction. Similarly, the positive terminal attracts the free holes in the p-type material, pulling them away from the junction. As a result, the depletion region widens.

2. Reduced Majority Carriers: The reverse biasing reduces the number of majority carriers (electrons in n-type and holes in p-type) near the junction. This reduction happens because the electric field created by the applied voltage pushes the majority carriers away from the junction, increasing the width of the depletion region.

3. Increase in Electric Field: The reverse biasing increases the strength of the electric field in the depletion region. As the width of the depletion region increases, the voltage across it also increases. This leads to a stronger electric field, which further widens the depletion region.

Conclusion:
When a p-n junction diode is reverse biased, the width of the depletion region increases due to the repulsion of free electrons and attraction of free holes. This widening of the depletion region plays a crucial role in blocking the flow of current in the reverse direction.

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