The depletion layer has large electrical resistance because:

The correct answer is Option (3) → It has no charge carriers.

The depletion layer forms when electrons and holes diffuse across the junction and recombine. The region near the junction is left with only immobile ions and is emptied of free electrons and holes. With no mobile charge to carry a current, it has a very large resistance.

Option (1) It contains few ions as charge carriers. — Incorrect. The ions in the depletion layer are fixed in the crystal and cannot move, so they are not charge carriers.

Option (2) It has few holes as charge carriers. — Incorrect. The holes in this region have recombined with electrons; the layer is depleted of holes, not left with a few of them.

Option (3) It has no charge carriers. — Correct. The layer is depleted of free charge carriers, so it hardly conducts.

Option (4) It contains few electrons as charge carriers. — Incorrect. The free electrons in this region have also recombined; the layer is depleted of them.

NCERT (2026-27):
p-n Junction Formation – “… This ionised donor (positive charge) is immobile as it is bonded to the surrounding atoms.”

p-n Junction Formation – “… This space-charge region on either side of the junction together is known as depletion region as the electrons and holes taking part in the initial movement across the junction depleted the region of its free charges (Fig. 14.10).”