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The conductivity of a semiconductor is generally intermediate, but varies widely under different conditions, such as exposure of the material to electric fields or specific frequencies of light, and, most important, with temperature and composition of the semiconductor material.
The amount of impurity, or dopant, added to an intrinsic (pure) semiconductor varies its level of conductivity. [26] Doped semiconductors are referred to as extrinsic. [27] By adding impurity to the pure semiconductors, the electrical conductivity may be varied by factors of thousands or millions. [28]
Also called chordal or DC resistance This corresponds to the usual definition of resistance; the voltage divided by the current R s t a t i c = V I. {\displaystyle R_{\mathrm {static} }={V \over I}.} It is the slope of the line (chord) from the origin through the point on the curve. Static resistance determines the power dissipation in an electrical component. Points on the current–voltage ...
For semiconductors doped through diffusion or surface peaked ion implantation we define the sheet resistance using the average resistivity ¯ = / ¯ of the material: = ¯ / = (¯) = (), which in materials with majority-carrier properties can be approximated by (neglecting intrinsic charge carriers): = (), where is the junction depth, is the ...
In solid-state physics, the valence band and conduction band are the bands closest to the Fermi level, and thus determine the electrical conductivity of the solid. In nonmetals, the valence band is the highest range of electron energies in which electrons are normally present at absolute zero temperature, while the conduction band is the lowest range of vacant electronic states.
The conductivity of a semiconductor can be modeled in terms of the band theory of solids. The band model of a semiconductor suggests that at ordinary temperatures there is a finite possibility that electrons can reach the conduction band and contribute to electrical conduction.
When light with sufficient energy hits a semiconductor, it can excite electrons across the band gap. This generates additional charge carriers, temporarily lowering the electrical resistance of materials. This higher conductivity in the presence of light is known as photoconductivity.
The Steinhart–Hart equation is a model relating the varying electrical resistance of a semiconductor to its varying temperatures. The equation is = + + (), where is the temperature (in kelvins), is the resistance at (in ohms),