Question

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

• 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 of the above

Answer 1

The correct option is C

Hole concentration in p-region is more as compared to n-region.

Explanation of correct option:-

Option (C):- Hole concentration in p-region is more as compared to n-region.

• In an unbiased diode, the electric field is set across the depletion layer which is between the n-type and p-type regions.
• This is because of the imbalance caused by the free electrons because of doping.
• Holes are the majority carriers in the p-region and electrons are the minority carriers.
• Electrons are the majority carriers in the n-region and holes are the minority carriers.
• Diffusion of charge carriers takes place between the junction of these two regions which happens from the region from higher concentration to the region of lower concentration
• So, holes diffuse from the p-region to the n-region.

Explanation of incorrect option:-

Option (A):- Free electrons in the n-region attract them.

• Electrons from the N-region do attract the holes.
• But, the movement of holes from the p-region to the n-region is because of the charge diffusion and the difference between the concentration of holes in both the regions.

Option (B):- They move across the junction by the potential difference

• The potential difference across the junction helps the minority carriers to move across.
• But holes are the majority carriers in the P-region.

Option (D):- All of the above

• Options (A) and (B) are not suitable for this question.
• So. “All of the above” can not be there.

Therefore, In an unbiased p-n junction, holes diffuse from the p-region to the n-region because hole concentration in p-region is more as compared to n-region

Hence, option (C) is correct.