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 in an unbiased p-n junction, we can break down the explanation into clear steps:

### Step-by-Step Solution:

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

**Hint:** Remember that p-type has holes (positive) and n-type has electrons (negative).

2. **Behavior of Charge Carriers:**
- In an unbiased p-n junction, there is no external voltage applied. However, there is still a natural movement of charge carriers.
- Holes from the p-side tend to diffuse into the n-side, while electrons from the n-side tend to diffuse into the p-side.

**Hint:** Think about diffusion as a process where particles move from an area of high concentration to low concentration.

3. **Formation of the Depletion Region:**
- As electrons and holes diffuse across the junction, they recombine, leading to a region near the junction that is depleted of charge carriers. This creates an electric field.
- The electric field results in a potential difference across the junction.

**Hint:** The depletion region is crucial for understanding how the junction operates.

4. **Potential Difference in the p-n Junction:**
- Due to the diffusion of charge carriers, the n-side becomes more negatively charged (higher potential) compared to the p-side, which becomes more positively charged (lower potential).
- Therefore, in an unbiased p-n junction, the n-side has a higher potential than the p-side.

**Hint:** Visualize the p-n junction as having a gradient of potential, where one side is more positive and the other is more negative.

5. **Conclusion:**
- Based on the above analysis, we conclude that in an unbiased p-n junction, the n-side is at a higher potential than the p-side.

**Hint:** Always refer back to the definitions of potential in terms of charge distribution when analyzing semiconductor devices.

### Final Answer:
In an unbiased p-n junction, the n-side is at a higher potential than the p-side.