When `p-n` junction diode is forward biased then

Options

A. the depletion region is reduced and barrier height is increased
B. the depletion region is widened and barrier height is reduced
C. both the depletion region and barrier height are reduced
D. both the depletion region and barrier height are increased

Answer

To solve the question regarding the behavior of a p-n junction diode when it is forward biased, we can analyze the effects of forward bias on the depletion region and the barrier height step by step.

### Step-by-Step Solution:

1. **Understanding the P-N Junction**:
- A p-n junction diode consists of p-type and n-type semiconductors. The p-type has an abundance of holes (positive charge carriers), while the n-type has an abundance of electrons (negative charge carriers).
- At the junction, electrons from the n-type region and holes from the p-type region recombine, creating a depletion region devoid of charge carriers.

2. **Forward Biasing the Diode**:
- Forward biasing occurs when the positive terminal of a voltage source is connected to the p-type material and the negative terminal to the n-type material.
- This external voltage opposes the built-in potential barrier of the junction.

3. **Effect on the Depletion Region**:
- When forward bias is applied, the external electric field generated by the voltage source reduces the width of the depletion region.
- The reason is that the external voltage pushes the holes towards the junction from the p-side and the electrons from the n-side, allowing more charge carriers to recombine and thus narrowing the depletion zone.

4. **Effect on the Barrier Height**:
- The potential barrier (or barrier height) is the energy required for charge carriers to cross the junction.
- With the application of forward bias, this barrier height decreases because the external voltage reduces the built-in potential barrier, making it easier for charge carriers to move across the junction.

5. **Conclusion**:
- Therefore, when a p-n junction diode is forward biased, both the depletion region and the barrier height are reduced.

### Final Answer:
The correct option is that both the depletion region and barrier height are reduced.

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