Semiconductors

A semiconductor is a material that is an insulator (electricity will not conduct; that is, electrons will not flow in it) at very low temperatures, but a fair (semi) conductor (electrons will flow in it) at room temperatures   The most common semiconductor is silicon.   When arsenic, boron, gallium, or phosphorus are added in small quantities as impurities ("doping") to ultrapure silicon, electrons can be made to flow in great quantities, over 100 x the amounts without the doping.

There are many semiconductors, such as germanium, silicon carbide, gallium arsenide, etc., each having special characteristics that serve specialized applications.   Semiconductors are made into semiconductor devices, such as transistors (amplifies or switches electricity), diodes (one-way electrical valve), and many others.   Thousands and even millions of these are combined into miniature integrated circuits that replaced the much larger vacuum tubes and wires that control and change electricity.   These miniature circuits and devices enable the construction of small, but extremely useful inventions, such as solar cells, microprocessors, miniature hearing aids, cellular phones, microwave ovens, and thousands of other products that contribute to higher living standards.

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