Barrier Potential in a PN Junction

Barrier Potential in a PN junction refers to the potential required to overcome the barrier at the PN junction.

When a P material and N material are brought in contact in a junction, some of the electrons of the N material near the junction cross over to the P material.  These electrons combine with the holes in the P material.  Similarly, the some of the holes of the P material near the Junction cross over to the N material and combine with the electrons.

The region in the contact area is thus depleted of holes and electrons.  This region is called the Depletion Layer.    The majority charge carriers are absent in this region.  This region almost becomes like an insulator.  Thus, there is no conduction after the depletion layer is formed.

For current to flow through this layer, a specific voltage has to be exceeded.  This is known as the barrier potential.  When an external voltage greater than the barrier potential is applied, the PN junction conducts.