Concept:n-type semiconductors are formed by doping a group 14 element (like silicon) with a pentavalent impurity that donates extra free electrons.
Explanation:Silicon has
4 valence electrons.
Phosphorous has
5 valence electrons.
When silicon is doped with phosphorous, four electrons form covalent bonds with neighbouring silicon atoms.
The fifth electron remains loosely bound and becomes a free electron, increasing conductivity.
Since the majority charge carriers are electrons, this creates an n-type semiconductor.
Boron and aluminium are trivalent (
3 valence electrons), producing p-type semiconductors instead.
Thus, the correct choice is silicon doped with phosphorous.
Answer:Option A: Silicon doped with phosphorous.