Question

Write the names of two important processes which occur on formation of p-n junction. Define the 'depletion region' and 'potential barrier' in it.

Answer 1

Two important process occurring in a p-n junction are diffusion and drift. When p and n sides come in contact, majority carriers diffuse from high concentration to low concentration. Electrons flow from n side to p side and combine with holes. Similarly holes from from p side to n side and combine with electrons near the junction. As this happens, region near junction gets depleted of carriers and gets charged to form a 'depletion region'. The diffusion of current leads to diffusion current.

The charge in depletion region forms electric field. The electric field leads to flow of minority carriers in the depletion region. This is called drift, and the formed current is drift current. Diffusion and drift current are opposite in direction.

The potential difference across depletion region due to electric field is called 'potential barrier'.