Hello,

I am using QuantumATK to model a 2D tellurium double-gate MOSFET, and I am running into some trouble with NEGF convergence when trying to obtain IV-characteristics. I have been working through the solutions discussed in the NEGF convergence guide article:

https://docs.quantumatk.com/technicalnotes/negf_convergence_guide/negf_convergence_guide.html, however, my convergence issues still persist. I’ve attempted to modify the channel and electrode length, experiment with the self-consistent loop parameters, and increase k-point grid density. Unfortunately, these haven’t improved the convergence issues significantly. Typically I can achieve convergence at the zero bias condition, though it takes quite a while to converge, and I haven’t been able to achieve convergence for the finite bias condition.

I’ve attached my atkpython script and log files for one of my attempts. I’m using the LCAO Calculator and running an IV sweep using the ivcharacteristics study object.

I’m still quite new to the QuantumATK software, so it’s also quite possible I’ve made a beginner’s error somewhere during the simulation setup.

It may also be worth mentioning that the MOSFET structure I’ve attached, which does not converge, has a 9 nm gate length. Previously, I was able to perform a fully converged IV sweep on a MOSFET device with a shorter 5 nm gate length. I’m not sure why increasing the gate length has resulted in these NEGF convergence issues. The same convergence issues appear when I try to include a gate underlap in the MOSFET structure.

If any assistance could be provided to resolve this convergence issue, it would be greatly appreciated!