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Electrical Properties: Conduction In Semiconductors

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Electrical Properties: Conduction In Semiconductors - Lesson Summary

Electrical conductivity of semi-conductors is very low. The addition of a small percentage of foreign atoms semi-conductor improves the electrical properties of semi - conductor.

Impurities introduce electronic defects in the semi-conductor, and produce an n-type or a p-type semi-conductor.


n-type semi-conductors: 
The addition of a pentavalent impurity such as antimony, arsenic or phosphorous contributes free electrons to the silicon or germanium lattice. This produces an n-type semi-conductor.

The free electrons contributed by the pentavalent impurity are responsible for conduction of electricity in an n-type semi-conductor.

p-type semi-conductors:
The addition of a trivalent impurity such as boron, aluminium or gallium to an intrinsic semi-conductor creates deficiencies of valence electrons.

One electron is missing from one of the four covalent bonds in the silicon crystal lattice. These are called holes.

Holes are the majority carriers, while electrons are the minority carriers in p-type semi-conductors. The direction of conduction of electricity is opposite to the movement of holes in P-type semiconductors.


Applications of p- and n-type semi-conductors:
The most important application is in a p-n junction diode. A photodiode converts light into electricity. The common, traditional solar cell used to generate solar power is actually a large-area photodiode.

Diodes are used in rectifiers. n and p semiconductors are used to make the transistor.

A large variety of compound semi-conductors, composed of elements from two different groups of the periodic table, such as 13-15 and 12-16, are widely used in communication devices. 

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