SEMICONDUCTORS

P-SEMICONDUCTORS:When a trivalent impurity is added to a tetravalent
semiconductor,it is called p-type semiconductor.If a trivalent
impurity like indium is added to germanium the indium atoms occupy
some of the sites at which three electrons form covalent bonds with
the adjacent germanium atoms because indium has three valence
electrons in outer most shell.The fourth covalent bond is incomplete
or empty,it creates an extra hole.By this way excess holes are formed
in this semiconductor, due to thermal energy conduction takes place in
valence band and conductivity of semiconductor increases.In p-type
semiconductor,holes are majority charge carriers and electrons are
minority charge carriers.In these semiconductors,Fermi energy level
will be nearer to the valence band.And the impurity is called acceptor
impurity.Indium,Gallium,Boron and Aluminium are the trivalent or
acceptor impurities which added to semiconductor materials. Posted by Unknown 18:02