Question

Depletion layer consists of:

• A. Electron
• B. Proton
• C. Mobile ions
• D. Immobile ions

Answer 1

The correct option is D Immobile ions

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.

Hence, $\left(D\right)$ is the correct answer.

Why this question? Note: The depletion layer consists of both electrons and protons, but they are immobile in nature, therefore the correct answer would be immobile ions.