Re: gEDA-user: OT diode reverse saturation current

[Andy Fierman <andyfierman@xxxxxxxxxxxxxxx>]

Hi Gene,

The usually quoted formula is:

IS = A*exp(-Eg/(k*T)

Where
IS = saturation current,
A is nearly constant independent of temperature and dependent on
diffusion coefficients of electrons and holes.
k is the Boltzmann constant. ν is a constant; 1 for germanium and 2
for silicon; and
T is the absolute temperature (deg Kelvin).
Eg is the band gap of the semiconductor. The band gap of silicon is
1.12eV and that of germanium 0.66eV.

According to this formula, IS doubles for approx 5degC rise in
temperature for silicon and 8degC for germanium.

However, the reality is somewhat different and a better
approximation(i) is this:

IS = A*T^m*exp(-Eg/(n*k*T))

Where
IS = saturation current,
A is a constant independent of temperature and dependent on diffusion
coefficients of electrons and holes.
k is the Boltzmann constant.
T is the absolute temperature (deg Kelvin).
m is a constant; 1.5 for silicon and 2 for germanium.
n is a constant; 1 for germanium and 2 for silicon
Eg is the band gap of the semiconductor. The band gap of silicon is
1.12eV and that of germanium 0.66eV.

I think the formula holds for GaAs and other semiconductor junction
diodes but the various constant will be different.

I'm not sure how IS varies for schottky (metal-semiconductor junction) diodes.

This also assumes that the reverse bias is not high enough to cause
any zener or avalanche breakdown effects that contribute to the
reverse leakage current.

Cheers,

         Andy.

www.signality.co.uk

(i) Integrated Electronics. Millman and Halkias (International Student
Edition) 1972 Lib
Cong Cat Card # 79-172657 p752 sect 19.11



2009/12/1 gene glick <carzrgr8@xxxxxxxxxxxxx>:
> I'm trying to find some info on the temperature variation of the reverse
> saturation current of a diode.  Anyone know about this?
>
> gene
>
>
> _______________________________________________
> geda-user mailing list
> geda-user@xxxxxxxxxxxxxx
> http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
>


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