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Any of various solid substances, such as silicon or germanium, that conduct electricity more easily than insulators but less easily than conductors. In semiconductors, thermal energy is enough to cause a small number of electrons to escape from the valence bonds between the atoms (the valence band); they orbit instead in the higher-energy conduction band, in which they are relatively free. The resulting gaps in the valence band are called holes. Semiconductors are vital to the design of electronic components and circuitry, including transistors, laser diodes, and memory and computer processing circuits.
electronic circuit component made from a material that is neither a good conductor nor a good insulator (hence semiconductor). Such devices have found wide applications because of their compactness, reliability, and low cost. As discrete components, they have found use in power devices, optical sensors, and light emitters, including solid-state lasers. They have a wide range of current- and voltage-handling capabilities, with current ratings from a few nanoamperes (109 ampere) to more than 5,000 amperes and voltage ratings extending above 100,000 volts. More importantly, semiconductor devices lend themselves to integration into complex but readily manufacturable microelectronic circuits. They are, and will be in the foreseeable future, the key elements for the majority of electronic systems, including communications, consumer, data-processing, and industrial-control equipment.