Question

Depletion layer consists of:

• A. electrons
• B. protons
• C. mobile ions
• D. immobile ions

Answer 1

Answer: (D)

The depletion layer consists of immobile ions because the depletion layer is formed by diffusion of holes and electrons from the $p$-type semiconductor to the $n$-type semiconductor, and vice versa.
Thus, donor and acceptor atoms gain positive and negative charges leading to $p$-n junction formation.
Thus, donor and acceptor are thus immobile ions.
Option A is incorrect because electrons can't reside inside the depletion region.
Option B is incorrect because proton doesn't reside inside the depletion layer.
Option C is incorrect because mobile ions can move but inside the depletion layer, ions can't movie.