Temperature dependence of drift and mobility characteristics of electrons
Author: Dattaraj Vidyasagar
When it comes to the mobility and drift factors of electrons, the electronics configuration of silicon has to be taken into consideration. The 3s-levels (all having same energy) in all N number of atoms, will have 2N number of electrons. But the 3p-levels (all having same energy), in all N number of atoms, which have a capacity of 6 electrons each, have only 2N number of electrons. Now suppose the natural (i.e. actual) interatomic separation between the Silicon atoms in the crystal is ‘a’ and all these atoms are brought closer to each other from the location ‘r’ to their actual position ‘a’, where r>> a, by gradually moving the atoms closer to each other. The conductivity (σ) of a semiconductor increases with increase in temperature: This is because more number of covalent bonds break and more number of free electrons are available for the conduction of electric current. The conductivity (σ) of conductors (metals) decreases with increase in temperature. Because as the temperature increases, the kinetic energy of free electrons increases. So the number of collisions between electrons and ions also increases. Due to this, the flow of current carriers is opposed, which increases the resistivity (ρ) of the metal. Hence, the conductivity of metals decreases with increase in temperature.
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