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fluxes in convection diffusion model

Posted 17 août 2016, 06:13 UTC−4 Semiconductor Devices Version 5.2 2 Replies

Jörg Buchwald
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Hey,
I'm trying to rebuild the semiconductor diode model from the comsol model library (v. 3.3) with comsol 5.2 and i have a problem concerning calculating the fluxes.
I used weak dirichlet bondary conditions and tried calculate the fluxes using the lagrange multipliers/the calculate boundary fluxes option. But the fluxes i get are neither conserved nor zero for the case where no voltage is applied, how can that happen within a stationary study?

Edit: Meanwhile, i rebuild the model in one dimension with comsol 4.4 and the problem still remains.
2 Replies Last Post 18 août 2016, 13:13 UTC−4
Jörg Buchwald
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Posted: 8 years ago 18 août 2016, 10:30 UTC−4
UPDATE i now tried a the same problem with smaller dimensions (length of diode 1e-7m) and the error vanishes. Obvisiously it seems to scale with the length dimensions, does anyone have an idea? The mesh element size does not seem to have a big impact. except for jumps that happen in the space dependent current density that are increasing with smaller element size. So it seems to be a numerical problem.
UPDATE i now tried a the same problem with smaller dimensions (length of diode 1e-7m) and the error vanishes. Obvisiously it seems to scale with the length dimensions, does anyone have an idea? The mesh element size does not seem to have a big impact. except for jumps that happen in the space dependent current density that are increasing with smaller element size. So it seems to be a numerical problem.
Jörg Buchwald
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Posted: 8 years ago 18 août 2016, 13:13 UTC−4
Problem solved by using the General Form PDE interface instead of the Convection-Diffusion module.
Problem solved by using the General Form PDE interface instead of the Convection-Diffusion module.

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