what is potential barrier in pn junction

A potential barrier is a region in a PN junction where the charge requires additional force to cross the region. When a P-type and N-type semiconductor material are placed together, a gradient of very large density charge carriers is created on both the P and N side region. The free electrons from the N-side cross the region and start combining with the holes, leaving behind the immobile positive donor ions. Similarly, the holes of the P-region combine with the electrons of the N-region and leaving behind the negative acceptor ions. The process is continued until the P and N-region have enough charge carrier for opposing the electrons and holes respectively. The immobile ions (negative acceptor ions and positive donor ions) are concentrated between the N and P-region and create the electric field which acts as a barrier between the flows of charges. The region is created because of the depleted ions, and hence it is called the depletion region. The depletion region acts as a barrier and opposes the flow of charge carrier. The value of barrier potential lies between 0.3 – 0.7V depending on the type of material used. When a forward bias is applied to a PN junction, it reduces the potential barrier.