The electrical resistance to the diffusion current in the depletion layer in a p-n junction is large due to the presence of
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → strong electric field
The depletion layer of a p-n junction contains immobile positive and negative ions, and these set up a strong electric field directed from the n-side to the p-side. This field acts as a potential barrier to the diffusion of the majority carriers (holes from p to n, electrons from n to p), so the diffusion current meets a large resistance.
Option (1) strong electric field — Correct. The built-in electric field of the layer opposes the diffusing carriers.
Option (2) large number of charge carriers — Incorrect. The layer is depleted of mobile carriers; it does not have a large number of them.
Option (3) electrons as charge carriers — Incorrect. Electrons are the diffusing carriers on one side, not what resists the diffusion.
Option (4) holes as charge carriers — Incorrect. Holes are likewise the diffusing carriers, not the cause of the resistance.