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Electron mobility

From Biocrawler, the free encyclopedia.

In physics, electron mobility (or simply, mobility), is used to describe the relation between drift velocity of electrons or holes in a solid material or electrons/ions in a gas, and an applied electric field. The drift mobility is directly related to the electric field as follows,

v d = μ E

where μ is the mobility.

In metric units, mobility is normally measured in cm²/V s. Since mobility is a strong function of impurities in a materials as well as temperature, it is difficult to provide any values of mobility here for common materials. Mobility is also different for electrons and holes in a semiconductor. When one charge carrier is dominant the conductivity of a semiconductor is directly proportional to the mobility of the dominant carrier.

Typical electron mobility for GaAs at room temperature is 2000 cm²/V s.

In approximation the mobility can be written as a combination of influences from lattice vibrations (phonons) and from impurities by following equation:

$\mu = \frac{1}{\frac{1}{\mu_{\rm lattice}}+\frac{1}{\mu_{\rm impurities}}}$ .