Source : WordNet®

semiconductor
     n 1: a substance as germanium or silicon whose electrical
          conductivity is intermediate between that of a metal and
          an insulator; its conductivity increases with
          temperature and in the presence of impurities [syn: {semiconducting
          material}]
     2: a conductor made with semiconducting material [syn: {semiconductor
        device}, {semiconductor unit}]

Source : Free On-Line Dictionary of Computing

semiconductor
     
         A material, typically crystaline, which allows
        {current} to flow under certain circumstances.  Common
        semiconductors are silicon, germanium, gallium arsenide.
        Semiconductors are used to make {diodes}, {transistors} and
        other basic "solid state" electronic components.
     
        As crystals of these materials are grown, they are "doped"
        with traces of other elements called {donors} or {acceptors}
        to make regions which are n- or p-type respectively for the
        {electron model} or p- or n-type under the {hole model}.
        Where n and p type regions adjoin, a junction is formed which
        will pass {current} in one direction (from p to n) but not the
        other, giving a {diode}.
     
        One {model} of semiconductor behaviour describes the doping
        elements as having either {free electrons} or {holes} dangling
        at the points in the crystal lattice where the doping elements
        replace one of the atoms of the foundation material.  When
        external electrons are applied to n-type material (which
        already has free electrons present) the repulsive force of
        like charges causes the free electrons to migrate toward the
        junction, where they are attracted to the holes in the p-type
        material.  Thus the junction conducts current.
     
        In contrast, when external electrons are applied to p-type
        material, the attraction of unlike charges causes the holes to
        migrate away from the junction and toward the source of
        external electrons.  The junction thus becomes "depleted" of
        its charge carriers and is non-conducting.
     
        (1995-10-04)