In the early 1900’s before integrated circuits and silicon chips were invented, computers and radios were made with vacuum tubes. This value permits the operation of silicon semiconductors devices at higher temperatures than germanium. Silicon is conventionally doped with Phosphorus, Arsenic and Antimony and Boron, Aluminum, and Gallium acceptors. It is a grey brittle material with a diamond cubic structure. Silicon belongs to the group IV in the periodic table. It is used for diodes, transistors, integrated circuits, memories, infrared detection and lenses, light-emitting diodes (LED), photosensors, strain gages, solar cells, charge transfer devices, radiation detectors and a variety of other devices. Silicon is the most common semiconductor material used today. Elemental semiconductors are simple-element semiconductor materials such as silicon or germanium. Semiconductors can be crystalline or amorphous. Semiconductors have electrical resistivity between 10-5 and 107 ohms. An important property of semiconductors is the ability to change their resistivity over several orders of magnitude by doping. Semiconductors are usually materials which have energy-band gaps smaller than 2eV. That is the equivalent of one tennis ball in a string of golf balls stretching from the earth to the moon. In this form, silicon is the purist industrial substance that man produces, with impurities comprising less than one part in a billion. It is extracted from rocks and common beach sand and put through an exhaustive purification process. It is the second most abundant substance on the earth. Silicon is the raw material most often used in integrated circuit (IC) fabrication.
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