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# Science Fair Project Encyclopedia

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# Electron mobility

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,

vd = μE,

where μ is the mobility.

In metric units, mobility is normally measured in cm2/Vs. 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.

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

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

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