nextnano.NEGF - Software for
Quantum Transport

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The following page (in construction) describes the simulation of devices with open boundary conditions such as RTDs with the nextnano.NEGF software.

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Note that in the current version (2020-11-19), only single band calculations are supported for open boundary conditions.
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====== Simulation of devices with open boundary conditions ======

In order to simulate a system with open boundary conditions (instead of the default field-periodic boundary condition), contacts have to be defined by adding a ''<Contacts>'' section in the input file:

<code>
<Contacts>
   <DensityLeft unit="cm^-3">1e18</DensityLeft>
   <DensityRight unit="cm^-3">1e18</DensityRight>
   
   <MaterialLeft>well</MaterialLeft>
   <MaterialRight>well</MaterialRight>

   <Broadening unit="meV">10.0</Broadening>
   <Ballistic>no</Ballistic>
</Contacts>
</code>

In this section, the carrier densities in the left and right contact have to been defined using the ''<DensityLeft>'' and ''<DensityRight>'' commands, as shown above. The unit is cm$^{-3}$.

The material of the left and right contacts needs to be defined by te command ''<MaterialLeft>'' and ''<MaterialRight>''. The string value has to be an alias defined in the ''<Materials>'' section of the input file.

A broadening energy can be defined by the command ''<Broadening>''. Indeed, scattering is not accounted in the contact, so that this commands allows a phenomenological broadening of the density of states in the contact.

The command ''<Ballistic>'' can be used to calculate ballistic transport between the contacts (i.e. no scattering process considered) if its value is set to ''yes''.

**The tutorial for AlGaAs/GaAs intraband RTD is available on our new manual from** [[https://www.nextnano.com/manual/nextnano.NEGF_tutorials/algaas_gaas_rtd.html|here]].

nextnano.NEGF - Software for Quantum Transport

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nextnano.NEGF - Software for
Quantum Transport