(a) state briefly the processes involved in the formation of p-n how the depletion region is formed
(b) using the necessary ciruit diagrams show p-n jucntion are obtained in
(i) forward biasing (ii) reverse biasing how these characteiistics are made use of in recitifcation

Explanation

Two processes occur during the formation of a p-n junction are diffusion and drift. Due to the concentration gradient across p and n-sides of the junction, holes diffuse from p-side to n-side (p `to` n) and electrons diffuse from n-side to p-side (n `to` p). This movement of charge carriers leaves behind ionised acceptors (negative charge `phi` - immobile) on the p-side and donors (positive charge immobile) on the n-side of the junction. This space charge region on either side of the junction together is known as depletion region.