I would like to modify the default equations in the semiconductor module

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I am planning to modify the default drift-diffusion equations under the Semiconductor Material Model. Also, I would like to add a new equation related to exciton concentration into the simulation.

Here are the equation I want to modify.

I read some of the post in the forum, and they said that I could modify the equations in the equation views panel. I have tried to understand the variables and weak formula in the equation view but I found that it was very complex. I want to find the weak expression or variables related to this equation, but I cannot find the ones correspond to this equation. Could anyone give me some hints how to modify the equation?

Also, I want to add a new equation related to the concentration of exciton. The equation is very similar to the drift-diffusion equation of electrons and holes. Is it possible for me to add some equation similar to the default drift-diffusion equation by using the PDE interface and couple it with the semiconductor module?


2 Replies Last Post Jul 9, 2020, 6:04 AM EDT

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Posted: 5 months ago Jul 8, 2020, 9:12 PM EDT

I believe sometimes you need to guess. Not everything is written in the documents.

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ZHANG, Pu
School of Physics,
Huazhong University of Science and Technology
I believe sometimes you need to guess. Not everything is written in the documents.

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Posted: 5 months ago Jul 9, 2020, 6:04 AM EDT

Hi Rui,

I believe the simplest way is indeed to use the PDE interface directly. You can recreate the drift diffusion equation quite easily using the "coefficient form PDE" physics for continuity equations, and "Poisson equation" physics for Poisson equation.

Then it is simply a matter of identifying the terms.

Note that there are some difference in implementation between the semiconductor module and the rest of COMSOL. You can read more about that in the manual of the module and decide for yourself if these differences matter to you.

If you intend to couple your semiconductor to an external circuit, I strongly advise that you look into the section named "Accurately computing fluxes" in the COMSOL user manual or the knowledge base.

Hi Rui, I believe the simplest way is indeed to use the PDE interface directly. You can recreate the drift diffusion equation quite easily using the "coefficient form PDE" physics for continuity equations, and "Poisson equation" physics for Poisson equation. Then it is simply a matter of identifying the terms. Note that there are some difference in implementation between the semiconductor module and the rest of COMSOL. You can read more about that in the manual of the module and decide for yourself if these differences matter to you. If you intend to couple your semiconductor to an external circuit, I strongly advise that you look into the section named "Accurately computing fluxes" in the COMSOL user manual or the knowledge base.

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