Question

In the depletion layer of a p-n junction diode, there are:

• A. only electrons
• B. only holes
• C. both electrons and holes
• D. neither electrons nor holes

Hint:

The depletion region is depleted of mobile carriers; only fixed ionised donor and acceptor atoms remain there.

Answer 1

The Correct Option is D

Step 1: Understand how the depletion layer forms.
When a p-type and an n-type semiconductor are joined, free electrons from the n-side diffuse across the junction and combine with holes on the p-side, while holes diffuse the other way and combine with electrons.

Step 2: See what is left behind near the junction.
This diffusion and recombination removes the mobile charge carriers (free electrons and holes) from a thin region on both sides of the junction. What remains there are only the fixed, immobile ionised donor atoms (positive) on the n-side and acceptor atoms (negative) on the p-side.

Step 3: Interpret the meaning of "depletion".
Because this region is depleted (emptied) of mobile charge carriers, it is called the depletion layer. It contains no free electrons and no free holes that can carry current; it has only the stationary lattice ions.

Step 4: Choose the correct option.
Since the region is free of mobile carriers, the correct answer is "neither electrons nor holes", option (iv). Options (i), (ii) and (iii) wrongly assume mobile carriers are still present.

\[\boxed{\text{Neither free electrons nor holes}}\]