| Electron Mobility |
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In Physics , electron mobility (or simply, '''mobility'''), is used to describe the relation between Drift Velocity of Electron s or Hole s in a solid material or electrons/ Ions in a gas, and an applied Electric Field . The drift velocity is directly related to the electric field as follows, :, where μ is the mobility. In Metric units, mobility is normally measured in Cm 2/( V · S ). Since mobility is a strong function of impurities 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 (300K) is 9200 cm2/(V·s). In approximation the mobility can be written as a combination of influences from lattice vibrations ( Phonon s) and from impurities by the following equation (Matthiessen's Rule): :. Mobility in gas phase Mobility is defined for any species in the gas phase, encountered mostly in Plasma physics and is defined as : where, q - charge of the species, - momentum transfer collision frequency, m - mass, Mobility is related to the species diffusion coefficient through an equation known as the '' Einstein Relation '': where, is Diffusion constant, is the mean free path, k - Boltzmann constant T - Species temperature EXTERNAL LINKS |
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