CHARGE CARRIER

any entity having electric charge, the motion of which constitutes an electric current. In metals the charge (or current) carriers are free electrons, common negative subatomic particles. In gases and liquids the charge carriers may also be positive and negative ions, atoms or molecules of the material that have a deficiency or an excess of electrons. In semiconductors the charge carriers are free electrons and holes. A hole, an absence of an electron in a bond between atoms, acts as a positive charge carrier and migrates through a current-carrying semiconductor in a direction opposite to the free electron drift. Positive current carriers may be distinguished experimentally from negative ones by the Hall effect (q.v.).