Question

The depletion layer in the p-n junction region is caused by

• A. migration of impurity ions
• B. drift of holes
• C. diffusion of charge carriers
• D. drift of electrons

Answer 1

Answer: (C)

diffusion of charge carriers

When a $p-n$ junction is formed, some of the free electrons in the $n$ region diffuses across the junction and combine with holes to form negative ions. In doing so they leave behind positive ions at the donor impurity sites. Similarly, holes from p side diffuse to the n side and thus form a layer called diffusion layer at the junction.

So the depletion region is caused by the diffusion of charge carriers.

Therefore option $C$ is correct.