Unique negative dimension

2012-02-04T13:26:58Z

93.135.33.97: Subcat

The '''saturation current''' or, more accurately, the '''reverse saturation current''' is that part of the reverse current in a [[semiconductor]] [[diode]] caused by diffusion of minority [[charge carrier|carriers]] from the neutral regions to the [[depletion region]]. This current is almost independent of the reverse voltage. (Steadman 1993, 459)

''I''S, the reverse bias saturation current for an ideal p–n [[diode]] is given by (Schubert 2006, 61):

<math>I_\mathrm{S} = e A \left( \sqrt{\frac{D_\mathrm{p}}{\tau_\mathrm{p}}} \frac{n_\mathrm{i}^2}{N_\mathrm{D}} + \sqrt{\frac{D_\mathrm{n}}{\tau_\mathrm{n}}} \frac{n_\mathrm{i}^2}{N_\mathrm{A}} \right),\,</math>

where
:''I''S is the reverse bias saturation current,
:''e'' is [[elementary charge]]
:''A'' is the cross-sectional area
:''D''p,n are the [[diffusion coefficient]]s of holes and electrons, respectively,
:''N''D,A are the donor and acceptor concentrations at the n side and p side, respectively,
:''n''i is the intrinsic carrier concentration in the semiconductor material,
:<math>\tau_\mathrm{p,n}</math> are the carrier lifetimes of holes and electrons, respectively.

Note that the saturation current is ''not'' a constant for a given device; it [http://www.pveducation.org/pvcdrom/solar-cell-operation/effect-of-temperature varies] with temperature; this variance is the dominant term in the temperature coefficient for a diode. A common rule of thumb is that it doubles for every 10°C rise in temperature. (Bogart 1986, 40)

==References==
* Steadman, J. W. (1993). "Electronics" in R. C. Dorf, ''The Electrical Engineering Handbook.'' Boca Raton: CRC Press.

* Schubert, E. Fred. (2006). "LED basics: Electrical properties" in ''Light-Emitting Diodes'' : Cambridge Press.

* Bogart, F. Theodore Jr. (1986). "Electronic Devices and Circuits" : Merill Publishing Company

{{DEFAULTSORT:Saturation Current}}
[[Category:Diodes]]

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2012-02-04T13:24:22Z

93.135.33.97: Subcat

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Unique negative dimension

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