electronics A material, typically crystaline, which allows
current to flow under certain circumstances. Common
semiconductors are silicon, germanium, gallium arsenide.
other basic "solid state" electronic components.
As crystals of these materials are grown, they are "doped"
to make regions which are n- or p-type respectively for the
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
One
model of semiconductor behaviour describes the doping
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)