I know that in p-n junction there is p type semiconductor in one side where there are majority holes and n-type semiconductor in another side where the majority charge carriers are electrons. Now during diffusion, electrons move from n-type to p-type and holes from p-type to n-type. My argument is I admit that since atom loses electron it becomes immovable positively charged ion and creates a region of positively charged ion in the near side of n type semiconductor. But it is found that nearby p-type semiconductor region of negative ions accumulate creating barrier voltage. I am confused how can there be region of negatively charged ions near p-type semiconductor as holes(positively charged) get neutralized by the electron. Please help.


1 Answer 1


Electrons of the conduction band of n side of the joint can lower its energy by migrating to the p-side, where there are available states (holes) in the valence band, with lower energy.

But the existence of that available states doesn't mean that p-side of the joint was positive charged. It was neutral before the electron migration.

After the migration, there is an excess of electrons at the p-side of the joint and a lack of electrons at the n-side.

So, there is an electrical field that balances the band structure tendency to migrating. When that E-field is strong enough, the migrating process is no more energetically favorable and the process stops, leaving what is called a depletion zone.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.