Comparison of DD_MS and NEGF_MS models for nanoscale SOI FET : Comparison of DD_MS and NEGF_MS models for nanoscale SOI FET

Requires: S-Pisces/Quantum
Minimum Versions: Atlas 5.24.1.R

This example demonstrates:

  • Comparison of quantum and classical transport models
  • Quantum confinement

This example compares classical drift-diffusion (DD_MS) and quantum (NEGF_MS) transport models in a 6nm thick Si SOI FET with 30 nm gate length. Both solutions employ uncoupled mode space approach, based on exactly the same Schrodinger and Poisson solvers and exactly the same material constants, and thus allowing a one-to-one comparison.

While it is generally accepted that a quantum transport solution should give slightly higher current due to source-to-drain tunneling (absent in DD_MS), the detailed comparison shows that other factors are more important. A comparison of eigen energy (bound state energy) profiles shows that a potential drop in the source in DD_MS model gives rise to a lower source injection barrier and higher classical current.

In addition, it is possible to look at the transmission function computed by NEGF and compare its steps with eigen energies at the source injection barrier. Once can see that transmission is non zero below the the maximum of eigen energy, which is due to source-to-drain tunneling. However, the magnitude of a single transmission step never reaches a value of one, which signals a strong reflection of electrons back into the source.

Slightly higher energy barrier and strong reflection lead to decrease of quantum current as compared to classical solution.

To load and run this example, select the Load button in DeckBuild > Examples. This will copy the input file and any support files to your current working directory. Select the Run button in DeckBuild to execute the example.