In an unbiased p-n junction, holes diffuse from the p-region ton-region because
(a) free electron in the n-region attract them.
(b ) they move across the junction by the potential difference.
(c ) hole concentration in p-region is more as compared to n-region.
(d ) All the above.

Options

A. free electrons in the n-region attract them.
B. they move across the junction by the potential difference.
C. hole concentration in p-region is more as compared to n-region
D. All the above

Answer

To solve the question regarding the diffusion of holes in an unbiased p-n junction, we can analyze the options provided:

1. **Understanding the p-n Junction**:
- A p-n junction is formed by joining p-type and n-type semiconductors. In the p-region, holes (positive charge carriers) are the majority carriers, while in the n-region, electrons (negative charge carriers) are the majority carriers.

2. **Analyzing Each Option**:
- **(a) Free electrons in the n-region attract them**: This statement is misleading. While electrons are present in the n-region, they do not specifically attract holes to diffuse across the junction.
- **(b) They move across the junction by the potential difference**: In an unbiased p-n junction, there is no external potential difference applied. The diffusion of holes is not driven by any potential difference but rather by concentration gradients.
- **(c) Hole concentration in p-region is more as compared to n-region**: This statement is true. Holes are indeed more concentrated in the p-region than in the n-region, which causes them to diffuse towards the n-region where the concentration is lower.
- **(d) All the above**: Since options (a) and (b) are incorrect, this option cannot be true.

3. **Conclusion**:
- The correct answer is **(c)**: Hole concentration in the p-region is more as compared to the n-region, which drives the diffusion of holes from the p-region to the n-region.

### Step-by-Step Solution:
1. Identify the components of a p-n junction (p-type and n-type).
2. Understand the role of majority carriers in each region (holes in p-region, electrons in n-region).
3. Evaluate each option provided in the question.
4. Determine that the only correct statement is that the hole concentration in the p-region is greater than in the n-region, leading to diffusion.
5. Conclude that the correct answer is option (c).