nextnano.NEGF is a tool designed for accurate quantum simulations of semiconducting devices using the Non-Equilibrium Green Functions (NEGF) formalism. It has been originally developed to simulate electron dynamics and gain in quantum cascade lasers (QCLs) and superlattices. It can also be apply to infrared detectors such as quantum well infrared detectors (QWIPs) and quantum cascade detectors (QCDs), as well as transport in resonant tunneling diodes (RTDs). It is progressively extended to further applications such as interband devices.
This simulation tool relies on the NEGF formalism, which has been shown to be a powerful framework to model quantum transport in presence of scattering processes.
- The following scattering mechanisms are included:
Longitudinal polar-optical phonon scattering (polar LO phonon scattering)
Acoustic phonon scattering
Charged impurity scattering
Interface roughness scattering
A possible application is illustrated below with the calculation of current-voltage characteristics in a QCL.
See also this video: nextnanoNEGF_video_ITQW_2017_1080p.mp4
We think it makes sense to
first get familiar with the nextnanomat user interface (using the nextnano++ software) and
then have a look at the nextnano.NEGF software.
You can solve the Schrödinger equation for a QCL heterostructure subject to an electric field using the nextnano++ software.
You can find simple QCL wave function calculation (including intersubband transition matrix elements) examples here:
C:\Program Files\nextnano\2020_12_09\Sample files\nextnano++ sample files\
Start with these input files:
1DQCL_simple_nnp.in, documented here:
THzQCL_Andrews_Vienna_MatSciEng2008_nnp.in, documented here:
Once you have gained some familiarity with the nextnanomat user interface, you can eventually start using the nextnano.NEGF software.
Install the nextnano software.
Once done, install the nextnano.NEGF software.
You can download the nextnano.NEGF software from here:
Unzip the file, store it to a useful location on your hard disk, and set the path to the
nextnano.NEGF.exe exectuable in
==> nextnano.NEGF executable file.
Please make sure to check in Windows File Explorer
==> File name extensions.
If you don’t check this option, you will only see:
nextnano.NEGF(without file extension
.exe.) and not
Sample input files can be found in the
\nextnano.NEGF sample files\ folder.
We recommend starting with this example:
THz_QCL_GaAs_AlGaAs_Fathololoumi_OptExpress2012_10K-FAST.xml and press the run button.
This is only a test file that runs fast (typically 10 minutes).
For reliable calculations, please use the corresponding file
which takes more CPU time (~12 hours) than
*FAST.xml but produces much more accurate results.
If the calculations take too long, your CPU might not be very fast or you do not have sufficient RAM.
In that case, please contact us.
You need at least 16 GB RAM, 32 GB are better.
Please note that you should run the larger input files on a computer having 32 GB RAM.
16 GB might be not enough and require a change in the settings for the number of parallel threads used for the gain calculation.
We recommend a Windows PC with 64 GB RAM, and a recent i7 CPU (e.g. a 6-core i7-8700).
The whole PC is then around USD 1,000.
If the software does not run, you might have to specify the
Material_Database.xml file in Tools
==> Material database.
We hope you enjoy using nextnano.NEGF. The technical part of the nextnano.NEGF software documentation is currently being updated and migrated to here from: https://www.nextnano.com/nextnano.NEGF/
Please let us know if you encounter any difficulty or notice any strange simulation results: Contact nextnano
Note also these slides on the implemented physics: http://iqclsw2018.lpa.ens.fr/IMG/pdf/tutorial_iqclsw_2018_grange.pdf