When a pure semicondutor is doped with an impurity the impure semicondutor thus obtained is called extrinsic semicondutor.

P type extrinsic semicondutor- When the impurity is of acceptor type (trivalent(4 minus 1) elements such as aluminium, boron, gallium etc), the extrinsic semiconductor is said to be of p-type as the majority carriers are holes which are positive in nature.

N type extrinsic semicondutor-When the impurity is of donor type (pentavalent(4 plus 1) elements such as arsenic, antimony,phosphorus etc) the extrinsic semiconductor is said to be of n-type as the majority carriers are electrons which are negative in nature.