When a p-type impurity is doped in a semiconductor,a large number of holes are created. This does not make the semiconductor chared.But when holes diffuse from the p-side to the n-side in a p-n junction,the n-side gets positvely charged.Explain.

Explanation

A p-type semiconductor is formed by doping a trivalent impurity element .With Si or Ge (Group 14 element ) . Group 13 element has only 3 electron in its valence shell, whereas group 14 one Si atom in its crystal only threee covalent bonds bond is left in the need of an electron .This result in creation of a hole . As the atom is electrically neutral so a p- type semconductor is also neutral.
When diffusion of hole takes place from p- side toward n-side then actually one valence electron to defficiency of electron n- side develops positive charge .