An extrinsic semiconductor is a type of semiconductor that has been intentionally doped with specific impurities to modify its electrical properties. This doping process introduces additional charge carriers—either electrons or holes—into the semiconductor material, thereby enhancing its conductivity.
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An extrinsic semiconductor has mobile electron and electron hole populations substantially controlled by electrically active impurities rather than solely by intrinsic thermal pair production. Donor impurities favor electron conduction and acceptor impurities favor hole conduction. Ionization, compensation and the temperature-dependent intrinsic population determine whether a given doped specimen is actually in its extrinsic transport regime.