semiconductor
<electronics> 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)
Nearby terms:
semi « Semi-Automatic Ground Environment « semicolon
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