Semiconductors: The Silicon Chip Essay

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Semiconductors: The Silicon Chip

Silicon is the raw material most often used in integrated circuit (IC) fabrication. It is the second most abundant substance on the earth. It is extracted from rocks and common beach sand and put through an exhaustive purification process. In this form, silicon is the purist industrial substance that man produces, with impurities comprising less than one part in a billion. That is the equivalent of one tennis ball in a string of golf balls stretching from the earth to the moon.

Semiconductors are usually materials which have energy-band gaps smaller than 2eV. An important property of semiconductors is the ability to change their resistivity over several orders of magnitude by doping. Semiconductors
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They began studying the electrical properties of semiconductors which are non-metallic substances, such as silicon, that are neither conductors of electricity, like metal, nor insulators like wood, but whose electrical properties lie between these extremes. By 1947 the transistor was invented. The Bell Labs research team sought a way of directly altering the electrical properties of semiconductor material. They learned they could change and control these properties by "doping" the semiconductor, or infusing it with selected elements, heated to a gaseous phase. When the semiconductor was also heated, atoms from the gases would seep into it and modify its pure, crystal structure by displacing some atoms. Because these dopant atoms had different amount of electrons than the semiconductor atoms, they formed conductive paths. If the dopant atoms had more electrons than the semiconductor atoms, the doped regions were called n-type to signify and excess of negative charge. Less electrons, or an excess of positive charge, created p-type regions. By allowing this dopant to take place in carefully delineated areas on the surface of the semiconductor, p-type regions could be created within n-type regions, and vice-versa. The transistor was much smaller than the vacuum tube, did not get very hot, and did not require a headed filament that would eventually burn out.

Finally in 1958,

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