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: Focus on the word depletion.
The very name of the layer tells the answer: to deplete means to empty out. So by definition this region has been emptied of something, and that something is the mobile charge carriers.

Step 2: Track where the carriers went.
Right after the junction is made, electrons near the boundary fall into nearby holes (recombination). Within a very thin strip, every free electron finds a hole and vice versa, so both disappear from that strip.

Step 3: Identify what stays.
The donor and acceptor atoms that gave up these carriers are now charged ions locked in the crystal lattice. They cannot move, so they form a fixed space-charge region and set up the built-in potential barrier, but they do not act as free carriers.

Step 4: Final answer.
Hence, inside the depletion layer there are no mobile electrons and no mobile holes available for conduction.

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