CBSE 2025, Set 3

Question

Explain the process of formation of 'depletion layer' and 'potential barrier' in a p-n junction region of a diode, with the help of a suitable diagram. Which feature of junction diode makes it suitable for its use as a rectifier?

Edvaya · Accepted Answer

The correct answer is Subjective. **Formation of Depletion Layer and Potential Barrier:**

![Depletion Layer Formation](https://www.edvaya.com/images/cbse/physics/2025/set3/q22-depletion-layer-formation-answer.webp)

1. **Diffusion:** Due to the concentration gradient across the p-n junction, electrons diffuse from the n-side to the p-side, and holes diffuse from the p-side to the n-side.
2. **Depletion Layer:** When an electron diffuses from the n-side, it leaves behind an uncompensated positively charged ionized donor atom. Similarly, a hole diffusing from the p-side leaves behind a negatively charged ionized acceptor atom. This space-charge region on either side of the junction, devoid of free mobile charge carriers, is called the **depletion layer**.
3. **Potential Barrier:** As the diffusion process continues, the accumulation of positive ions on the n-side and negative ions on the p-side creates an electric field directed from n to p. This field exerts a force on the majority carriers, opposing further diffusion. The potential difference associated with this electric field, which prevents the further movement of majority carriers across the junction, is called the **potential barrier**.

**Feature for Rectification:**
A junction diode is suitable for use as a rectifier because it is **unidirectional**. It offers low resistance and allows current to pass only when it is forward-biased, while it offers very high resistance and blocks current when it is reverse-biased.

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Physics > Modern Physics > Semiconductor Electronics

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