Cambridge Encyclopedia » Cambridge Encyclopedia Vol. 67

semiconductor - Overview, Band structure, Carrier generation and recombination, Doping, Preparation of semiconductor materials

silicon conductivity type semiconductors

A substance whose electrical conductivity is between that of an insulator and a conductor at room temperature. The conductivity can be made to vary with temperature and the impurities in the semiconductor crystal. In intrinsic semiconductors, usually made from pure crystals of germanium or silicon (known as semi-metals), conductivity rises with temperature. The conductivity of extrinsic semiconductors depends on introducing impurities into intrinsic semiconductors - a process known as ‘doping’. If arsenic or phosphorus is added (which have more electrons than the silicon) the semiconductor becomes known as an n-type (a negative carrier of electricity). If silicon is doped with elements such as boron or aluminium (which have fewer electrons in their atoms than silicon), a p-type (positive) semiconductor is created, containing conductive holes. Typical semiconductor devices such as diodes and transistors (combinations of p- and n-types) have different arrangements of impurities. Gallium arsenide is the newest and fastest type of semiconductor, and has replaced silicon in many microchips.

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