Mumbai university > FE > SEM 1 > Applied Physics 1

Marks: 5M

Year: Dec 2013

When a p-n junctio is formed, some free electrons from the n-type semiconductor cross the junction and fill the vacant space in the p-type junction.

• This vacant space which was initially a hole, once filled with the electron, the incomplete bond with a neighbouring silicon atom of the impurity atom is completed.

• As a result, the electron from the n-type region is now immobile.

• At the same time, due to lack of electrons in the n-type region, we can say that a positively charged hole is migrated to the n-type region.

• Since, initially both the sides were electrically neutral and because of the migration of charge carriers, the n-type region near interface develops a slight positive charge(tδ)

• Similarly, p-type region near the interface develops a slight negative charge(- δ)

• As these regions contain immobile charges, the region is called the Depletion Region.

• Due to the slight charges developed at the interface, further migration of the charges is stopped.

• The potential difference generated by these migrated charges is called Barrier Potential.