SEMICONDUCTORS and S E M I C O N D U C T I VIT Y
All substances have some ability to conduct electric current however, thejrdiffer in the ease with which the current can pass throug them. Metals such as copper, gold, silver or iron are excellent conductors of electric current whereas materials such as glass, porcelain, polystyrene, rubber, or quartz are considered to be excellent insulatorsPlntermediate between the two groups are semiconductor materials, i.e.. those which have a conductivity intermediate between that of an insulator and that of a metal. They include all minerals, many chemical elements, a great variety of chemical compounds, alloys of metals, and a number of organic compounds.
The semiconductors such as silicon, germanium, selenium, phosphorium, boron and various other metallic oxides and sulphides appear to possess some unexpected properties. For instance, their conductivity increases with heating and falls with cooling. However, heat is not the only phenomenon influencing semiconductors . They are sensitive to light, radiation, too.
Some of the properties which are now associated with semiconductors have been known for a century or more. But a great deal of experimental work had to be carried out before scientists were able to explain the phenomenon of semiconductivity.
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