In an unblased p-n junction, holes diffuse from the p - region to n- region because

Options

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

Explanation

To solve the question regarding why holes diffuse from the p-region to the n-region in an unbiased p-n junction, we can follow these steps:

### Step 1: Understand the Structure of a p-n Junction
A p-n junction is formed by joining p-type and n-type semiconductors. In the p-type region, there are more holes (positive charge carriers) than electrons, while in the n-type region, there are more electrons (negative charge carriers) than holes.

**Hint:** Remember that p-type semiconductors have an abundance of holes, while n-type semiconductors have an abundance of electrons.

### Step 2: Define Unbiased p-n Junction
An unbiased p-n junction means that no external voltage is applied across the junction. This condition allows for the natural diffusion of charge carriers due to concentration gradients.

**Hint:** An unbiased p-n junction does not have any external forces acting on it, allowing the natural movement of charge carriers.

### Step 3: Analyze Carrier Concentrations
In the p-region, the concentration of holes is higher than that in the n-region. This difference in concentration creates a gradient, prompting holes to diffuse from the p-region to the n-region.

**Hint:** Concentration gradients drive the diffusion of charge carriers from areas of high concentration to areas of low concentration.

### Step 4: Identify the Mechanism of Diffusion
Holes move from the p-region to the n-region because they are attracted to the electrons present in the n-region. However, the primary reason for their movement is the higher concentration of holes in the p-region compared to the n-region.

**Hint:** While attraction to electrons plays a role, the primary driving force for diffusion is the difference in hole concentration.

### Step 5: Conclusion
The correct answer to the question is that holes diffuse from the p-region to the n-region because the hole concentration in the p-region is greater than in the n-region.

**Final Answer:** Holes diffuse from the p-region to the n-region because the hole concentration in the p-region is more compared to the n-region.