Stiffness/Residual Vector Error - NaN/Inf findings

[Bera Icli]

Hi,

I am especially writing this, because there is no specific explanation I found online. I checked the BCs and other variables, but could not find any mistakes.

I am working on a semiconductor device that is basically n-doped homogeneously, has sizes 50um-15nm, and with a drain voltage 1V on the left boundary, source voltage 0V on the right, and a varying gate voltage at its top with a thin insulator gate of. Although I work on a supercomputer with 36gb ram, and making a mesh not much detailed, I gather the error attached as image.

The error does not happen when I sweep the gate voltage from around -13V to 20V, but whenever I start it from around -15V it just happens. The error contains NaN/Inf findings in the solution, not a convergence error or a iteration one I guess, but somehow a calculation error. The simulation works well for -13V to 20V of gate voltage, giving a nice plot, but not for below -13V.

Sometimes it is an undefined value in stiffness vector, sometimes a residual vector error.

I want to plot the ID-VG graph accordingly, but cannot see below -13V. Can't I simulate after some voltage level?

Any comments for a better simulation?

Thanks,

~bera

 

[DrClaude]

The amount of information you gave about what you are doing is minuscule. I don't see how anyone could help you, since you don't even mention which program you are using (I would guess COMSOL from the screenshot), nor what you are solving for.

 

[Bera Icli]

Thank you for replying DrClaude. Yes, unfortunately it escaped my notice while writing the post, I am using COMSOL 5.0. I hope someone can help me out with this. Although it seems COMSOL will not be capable of solving while sweeping below a specific voltage from gate insulator, I hope my problem will be either solved or commented as an insoluble problem.

Is that possible to solve the problem as indicated in the screenshot and continue to keep solve below some voltage level as well.