In an unbiased p-n junction which of the following is correct?

Options

A. p-side is at higher potential than n-side
B. n-side is at higher potential than p-side
C. Both p-side and n-side are at the same potential
D. Any of the above is possible depending upon the carrier density in the two sides.

Answer

To solve the question regarding the potential difference in an unbiased p-n junction, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Structure of a p-n Junction**:
- A p-n junction is formed by joining p-type and n-type semiconductors. The p-type semiconductor has an abundance of holes (positive charge carriers), while the n-type semiconductor has an abundance of electrons (negative charge carriers).

2. **Behavior of Charge Carriers**:
- When the p-n junction is formed, holes from the p-side diffuse into the n-side and electrons from the n-side diffuse into the p-side. This movement of charge carriers leads to the formation of a depletion region at the junction.

3. **Formation of the Depletion Region**:
- The diffusion of holes and electrons creates a region devoid of mobile charge carriers, known as the depletion region. In this region, the p-side becomes positively charged (due to the presence of fixed positive ions left behind after holes leave) and the n-side becomes negatively charged (due to the presence of fixed negative ions left behind after electrons leave).

4. **Electric Field and Potential Difference**:
- The charge separation in the depletion region creates an electric field pointing from the n-side to the p-side. This electric field indicates that the n-side has a higher potential compared to the p-side.

5. **Conclusion**:
- Based on the above analysis, in an unbiased p-n junction, the n-side is at a higher potential than the p-side. Therefore, the correct answer to the question is **Option 2: n side is higher potential than p side**.

### Final Answer:
The correct option is **Option 2: n side is higher potential than p side**.

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