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 battier 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 break it down into a series of logical steps.

### Step-by-Step Solution:

1. **Understanding the p-n Junction**:
- A p-n junction diode consists of two types of semiconductor materials: p-type (positive) and n-type (negative). The p-type has an abundance of holes (positive charge carriers), while the n-type has an abundance of electrons (negative charge carriers).

2. **Forward Biasing the Diode**:
- When a p-n junction diode is forward biased, the positive terminal of the battery is connected to the p-type material, and the negative terminal is connected to the n-type material. This arrangement reduces the potential barrier that exists at the junction.

3. **Effect on Depletion Region**:
- In the absence of an external voltage (when the diode is off), there exists a depletion region at the junction where mobile charge carriers (electrons and holes) are absent. This region acts as a barrier to current flow.
- When the diode is forward biased, the applied voltage reduces the width of the depletion region. This is because the external voltage pushes holes from the p-side towards the junction and electrons from the n-side towards the junction, allowing them to recombine.

4. **Reduction of Barrier Height**:
- The barrier height is the energy barrier that must be overcome for charge carriers to move across the junction. When forward bias is applied, this barrier height decreases, making it easier for electrons and holes to recombine and thus allowing current to flow through the diode.

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

### Final Answer:
- The correct answer is that both the depletion region and the barrier height will be reduced when the p-n junction diode is forward biased.