Saturation current is a term used in relation to semiconductor diodes. It is more fully, and accurately, named reverse saturation current and is "part of the reverse current in a diode caused by diffusion of minority carriers from the neutral regions to the depletion region. This current is almost independent of the reverse voltage." (Steadman 1993, 459)
IS, the reverse bias saturation current for an ideal p-n diode is given by, (Schubert 2006, 61)
where
- IS is the reverse bias saturation current,
- e is elementary charge
- A is the cross-sectional area
- Dp,n are the diffusion coefficients of holes and electrons, respectively,
- ND,A are the donor and acceptor concentrations at the n side and p side, respectively,
- ni is the intrinsic carrier concentration in the semiconductor material,
- are the carrier lifetimes of holes and electrons, respectively.
Note that the saturation current is not a constant for a given device; it varies with temperature; this variance is the dominant term in the temperature coefficient for a diode.
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