DEVICE charge simulation : a symmetric structure has a asymmetric carries distribution


#1

Hello!:
I am simulating the TCO(Transparent Conducting Oxide)-based modulator. There is a paper may be help ().It works on the change of the carrier(like MOS capacitancTransparent conducting oxide electro-optic modulators on silicon platforms A comprehensive study based on the drift-diffusion semiconductor model.pdf (3.4 MB) when apply different volage which leads to the change of permitity.I has succeeded to get expected results when the HfO2 layer is 5nm(like Fig1.5nm HfO2), however, when I change it to 10nm the carries distributy is like fig2.10nm HfO2 .You may find it is not symmetric between the right and left.So could you help me to find the problem? May be dopping incorrect or meshing unproperly. Thank you a lot!
Regards!

Fig1 5nmHfO2

Fig2 10nm HfO2
TCO modulator change HfO2 10nm 0-7V 0.25V.ldev (6.4 MB)


#2

Thanks for sharing the simulation files. I believe the reason your result does not look symmetric in because the mesh is not. If you look at the screenshot of the mesh below you can see that the HfO2 layer got pretty well refined in the top and left wall but not on the right wall.

This difference in the mesh is most likely resulting in a result that is not symmetric. Now the reason behind the mesh not getting refined properly is because your solver is reaching the maximum number of iteration while refining the mesh and is stopping before the mesh is completely refined. If you look at the log file you will notice the following warning messages:

"Generating mesh.
Refinement limit exceeded for auto-refinement. The mesh is valid but may not be adequately refined.
Refinement limit exceeded for auto-refinement. The mesh is valid but may not be adequately refined.
Refinement limit exceeded for auto-refinement. The mesh is valid but may not be adequately refined.
Mesh generation complete (15s)

  • vertices: 78124
  • elements: 156137"

This incident has been discussed in the following KX post (How to resolve warning message: “The mesh is valid but may not be adequately refined”). Please take a look at the post to learn how you can refine the mesh completely. I believe that once the mesh is completely refined the result will look symmteric since yo have a completely symmetric structure here.