Q.What is meant by doping a semiconductor? Distinguish between a pentavalent and a trivalent dopant, giving one example of each and naming the type of extrinsic semiconductor each produces.

Deliberately adding a controlled trace of a chosen impurity atom to an intrinsic semiconductor. A PENTAVALENT dopant (Group 15: P, As, Sb) donates a loosely bound spare electron beyond the four needed for covalent bonding, becoming a fixed positive donor ion and producing an n-type semiconductor (majority carriers: electrons). A TRIVALENT dopant (Group 13: B, Al, Ga, In) leaves one covalent bond incomplete, readily accepting a neighbouring electron, becoming a fixed negative acceptor ion a …