Physical process of depletion layer.

Physical Process of Depletion Layer- We know that a p-type materials has holes as majority carriers negatively charged impurity atoms called negative ions (or acceptor ions). The n-type material has free electrons as  majority carriers and positively charged impurity atoms called positive ions (or donor ions). When we combine these two materials, following process takes place-

(i)The holes from p-region diffuse to the n-region where they combine with the free electrons.
(ii) The free electrons from the n-region diffuse to the p-region where they combine with holes.
(iii) The diffusion of holes (from p-region to n-region) and free electrons (from n-region to p-region) takes place due to the reason that there is a difference of concentrations in the two regions. (iv) The diffusion of holes and electrons across the junction takes place for a short time. After a few recombination of holes and free electrons in the vicinity of the junction, a restraining force is automatically Setup This force is produced due to depletion région. which exists on either side of the junction. As result of this further diffusion of holes and free electrons from a one region to the other is stopped by this depletion layer.