Why can't we physically join p-type and n-type semiconductors directly to form a p-n junction? Why the depletion layer widens on doing so?

Asked by Aswin | 14th Jan, 2016, 05:21: PM

Expert Answer:

A pn junction works if there is a continuous structure when joined.
If we physically join the two semiconductors, then there will always be very small microscopic gap or dicontinuity between the two because of roughness.
A p-type semiconductor has holes as majority carriers and the n-type semiconductor has electrons as majority. When a pn junction is formed, the holes from p and electrons from n move to the other type and hence, the width of the depletion layer widens.

Answered by Romal Bhansali | 15th Jan, 2016, 12:07: PM