Divergence caused by High field mobility ?

- September 27, 2022 at 6:25 am
  
  Mariah Ha
  Subscriber
  
  Hi ,
  I have had a divergence problem in Charge for a long time and I inspected every aspect of the simulation (smaller mesh, convergence solver, gradient mixing, initialization, more iterations .....). The problem is because of using the high field mobility in the mobility model. However, I still would like to use the high field mobility in my model. Are there any recommendations on how troubleshoot the convergence issue in my case?
  I am simulating a photodiode in 3D.
  Thank you.
  Regards.
- September 27, 2022 at 4:59 pm
  
  Guilin Sun
  Ansys Employee
  
  When the high field mobility is enbaled, many a time the simulation can diverge, due to some reasons. I would suggest to read this article: https://optics.ansys.com/hc/en-us/articles/8355464963987-Troubleshooting-convergence-errors-in-CHARGE It has some solutions for this case.
  Have you tested zero bias? if it can run successfully, it means the field might be too high and finer mesh is needed.
  When you sweep the voltage, please try to use smaller voltage step.
  
  If the zero bias cannot converge, please first disable the high field mobility, and do a test. Then plot the fields and see where the high field is located. Then add "constraint" mesh to limit its largest edge length. Repeat the above tests again.