Question

Depletion region in an unbiased semiconductor diode is a region consisting of

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

Answer 1

The Correct Option is B

The depletion region in an unbiased semiconductor diode is formed due to the diffusion of electrons and holes. In this region, the free electrons from the n-type region recombine with holes from the p-type region. This process leaves behind a region that is depleted of free charge carriers, meaning there are neither free electrons nor holes in this area. The region contains immobile ionized donor and acceptor ions.  

Thus, the depletion region consists of neither free electrons nor holes.  

Therefore, the correct answer is (B) neither free electrons nor holes.

Answer 2

In an unbiased semiconductor diode, the depletion region is formed at the junction between the p-type and n-type materials. This region is depleted of free charge carriers (both free electrons and holes) because, at the junction, the free electrons from the n-side diffuse to the p-side and combine with holes, forming immobile ionized donor and acceptor ions. These ions create an electric field that prevents further diffusion of charge carriers across the junction. As a result, the depletion region does not contain free electrons or holes but consists of immobile ions, leaving it electrically neutral.

Therefore, the correct answer is that the depletion region consists of neither free electrons nor holes.