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There are two recognized types of charge carriers in semiconductors.One is electrons, which carry a negative electric charge.In addition, it is convenient to treat the traveling vacancies in the valence band electron population as a second type of charge carrier, which carry a positive charge equal in magnitude to that of an electron.
Depending on the model, increased temperature may either increase or decrease carrier mobility, applied electric field can increase mobility by contributing to thermal ionization of trapped charges, and increased concentration of localized states increases the mobility as well. Charge transport in the same material may have to be described by ...
The resulting average drift mobility is: [20] = ¯ where q is the elementary charge, m* is the carrier effective mass, and τ is the average scattering time. If the effective mass is anisotropic (direction-dependent), m * is the effective mass in the direction of the electric field.
In solid-state physics of semiconductors, carrier generation and carrier recombination are processes by which mobile charge carriers (electrons and electron holes) are created and eliminated. Carrier generation and recombination processes are fundamental to the operation of many optoelectronic semiconductor devices , such as photodiodes , light ...
The drift velocity is the average velocity of the charge carriers in the drift current. The drift velocity, and resulting current, is characterized by the mobility; for details, see electron mobility (for solids) or electrical mobility (for a more general discussion).
Charge carrier density, also known as carrier concentration, denotes the number of charge carriers per volume. In SI units, it is measured in m −3. As with any density, in principle it can depend on position. However, usually carrier concentration is given as a single number, and represents the average carrier density over the whole material.
Electrical mobility is the ability of charged particles (such as electrons or protons) to move through a medium in response to an electric field that is pulling them. The separation of ions according to their mobility in gas phase is called ion mobility spectrometry, in liquid phase it is called electrophoresis.
In general, carriers will exhibit ballistic conduction when where is the length of the active part of the device (e.g., a channel in a MOSFET). λ M F P {\displaystyle \lambda _{\rm {MFP}}} is the mean free path for the carrier which can be given by Matthiessen's rule , written here for electrons: