The depletion layer in PN junction diode is caused by (A) drift of holes (B) Diffusion of impurity ions (C) diffusion of charge carriers (D) drift of electrons

A PN junction diode is a semiconductor device formed by joining a P-type semiconductor (which contains an excess of holes) and an N-type semiconductor (which contains an excess of electrons). In this diode, a junction is formed at the interface between the two types of materials, resulting in specific electrical characteristics.

The depletion layer is an insulating region that forms at the junction of a PN diode, where the P-type and N-type materials meet. This layer is formed due to the diffusion of charge carriers (holes from the P-type region and electrons from the N-type region) across the junction. As these charge carriers move, they leave behind fixed impurity ions, creating a region with no free charge carriers. This region is known as the depletion layer because it is depleted of mobile charge carriers.

(A) Drift of holes: Drift is the movement of charge carriers (holes or electrons) due to an electric field. While drift occurs in semiconductors, it is not the main cause of the depletion layer in a PN junction diode. (B) Diffusion of impurity ions: Although the diffusion of charge carriers forms the depletion layer, it is not due to impurity ions. It is primarily due to the diffusion of holes and electrons. (C) Diffusion of charge carriers: This is the main cause of the depletion layer in a PN junction diode. The diffusion of holes and electrons from their respective semiconductor regions across the junction creates the insulating depletion layer. (D) Drift of electrons: Similar to option (A), drift is not the primary cause of the depletion layer in a PN junction diode. Therefore, the correct answer is (C) diffusion of charge carriers.