Question

Initially, during the formation of a p-n junction:

• A. Diffusion current is large and drift current is small.
• B. Diffusion current is small and drift current is large.
• C. Both the diffusion and the drift currents are large.
• D. Both the diffusion and the drift currents are small.

Hint:

In a p-n junction, diffusion current dominates initially, but as the depletion region builds up, drift current increases to balance it.

Answer 1

The Correct Option is A

Understanding Current Flow in p-n Junction Formation
- In a newly formed p-n junction, a concentration gradient exists between the p-region and n-region.
- This causes majority charge carriers (electrons from n-region and holes from p-region) to diffuse across the junction, leading to a large diffusion current.
- As electrons and holes diffuse, a depletion region forms, creating an internal electric field.
- This electric field generates a small drift current by moving minority carriers in the opposite direction.
- Over time, the diffusion current and drift current balance each other at equilibrium. Thus, during the initial formation of the p-n junction, the diffusion current is large, and the drift current is small.