Hi Ahsan,

I enabled the “impact ionization” and made all the modifications you mentioned above. Unfortunately after about 10-hour simulation, it failed to converge again. Here’s the error message:

```
...
Generating mesh.
Refinement limit exceeded for optical generation rate constraint. The mesh is valid but may not be adequately refined.
Mesh generation complete (13s)
+ vertices: 30981
+ elements: 121149
All processes are communicating and ready to proceed to simulation...
Starting solver.
Solver terminated at step 1 of 1. Error (charge): Drift-diffusion solver failed to converge after 40 iterations, 3.03816e+52(0.0001) remains. Residual (ratio/last) 1.58245e+25/1.04638e+23.
Warning: the charge transport solver failed to converge. A partial result will be saved.
The program terminated due to an error: The simulated result is incomplete. Please review the log files for details.
Error: there was an unknown parallel error. The error code is 9002, the process number is 0
```

I set the boundary condition to be “cathode = 0V, anode = -10V”, and run single-point DC simulation. I guess starting from some smaller bias may help in terms of convergence, but I really don’t care about the electrical field distribution at moderate reverse bias voltage (let alone the simulation time is incredibly long). In addition, I sort of believe the diode hasn’t broken down at 10V bias. Are there any other changes I can make to help converge?

According to one of your previous posts:

Since the solver will sweep anyway, is it possible to know at what voltage my simulation fails to converge?

Also, even the simulation fails, I still manage to get all the results I want (and they looks reasonable!) Could you please shed some light on this?

Thanks in advance!

(By the way, since this time the error message becomes “Drift-diffusion solver failed to converge”, I am not sure if it’s still suitable to post the question here. If not, please help me redirect it. Thanks.)