SOLUTION

The depletion region is created by Diffusion and Recombination.

Detailed Explanation

As soon as a PN junction is formed, electrons frog n-type material diffuse into p-type material and fill some of the holes there.

When the junction is formed, the following processes are initiated:

⇒ Holes from the P side diffuse into the N side, where they combine with free electrons.

⇒ Free electrons from the N side diffuse into the P side, where they combine with holes.

⇒ The diffusion of holes and electrons is an electric current is referred to as a ‘recombination current.‘ Most of the recombination occurs soon after the junction is formed, in the region very near the junction.

⇒ Diffusion is a process where charges move from higher concentration to lower concentration with or without the influence of the field.

⇒ They are responsible for charge movement through the junction.

⇒ Finally, recombination is a process where the electrons and holes neutralize charged atoms. So, diffusion results in recombination which creates a depletion region.