Zero bias transmission

[AsifShah]

Dear Admin,
Does zero bias transmission include scattering across an interface with defect or it is ballistic?

If ballistic, why am I observing an increase of transmission in conduction and valence bands with defect at interface with respect to pristine interface?

[Anders Blom]

The term "ballistic" is somewhat ambiguous. In our NEGF mode it's taken to mean the opposite of diffusive (as in "ballistic transport", below the mean free path, i.e. no energy relaxation from phonon scattering), since we include scattering of interfaces, defects, surface roughness, etc as created by any atom not in a perfectly periodic arrangement. In some other models i's defined it as "no scattering at all", which would only be possible in a perfect crystal, and thus is rather uninteresting in an atomistic picture, but makes sense in higher-level models when you only use the mobility or set transmission to 1 to model a ballistic conductor.

No matter the bias, the transmission spectrum is computed including the effects of all atoms present in the system.

[AsifShah]

Dear Ander Bloms,

Thanks for your response. I still have a doubt, when you say QATK includes the effects of all atoms, "Does that mean it takes account of an electron scattering from energy E1 to E2? In other words, if an electron is traveling with energy E1 from the electrode and encounters a scatterer in the central region taking it to energy E2, will such an event be included in the transmission calculated from QATK?"

[Anders Blom]

No, all transport we compute is elastic by default. Otherwise you would have to introduce extra effects that take/give the energy the electron loses/gains in the process. This could be phonons, and QuantumATK can handle inelastic phonon scattering, see corresponding tutorials on that, like https://docs.quantumatk.com/tutorials/inelastic_current_in_si_pn_junction/inelastic_current_in_si_pn_junction.html.

[AsifShah]

Thanks