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For each simulation run, a new output folder is created in the simulation output folder. The created folder has the name of the input file. In addition date-time is added to the folder name if the option is selected in Options→Expert settings of nextnanomat (this option is recommended in order to avoid overwritten existing output data). The created output folder contains:
The folder Input/
contains all information that is input to the simulation such as material parameters.
AlloyContent.dat
Al(x)Ga(1-x)As
BandEdge_conduction.dat
BandEdges.dat
BandGap.dat
DeformationPotential_ConductionBand.dat
EffectiveMass.dat
ElasticConstants.dat
EpsOptic.dat
EpsStatic.dat
LatticeConstants.dat
MaterialDensity.dat
PhononEnergy_LO.dat
PiezoConstants.dat
PyroConstants.dat
VelocityOfSound.dat
If the strain option is activated, a folder Strain/
is created containing the strain tensor components $\epsilon_{ij}$ which are dimensionless.
Strain_CrystalSystem.dat
Strain_Simulation.dat
If the crystal has not been rotated, both files contain identical values.
The folder Polarization/
contains the piezoelectric and pyroelectric polarization if these options are activated.
PiezoChargeDensity.dat
PyroChargeDensity.dat
The folder Init_Electr_Modes/
contains 3 different folders corresponding to the different sets of basis states. They correspond to the initial solution of the Schrödinger equation without accounting for Poisson equation (i.e. electrostatic mean-field) nor scattering self-energies.
The folder Init_Electr_Modes/ReducedRealSpace/
contains:
ReducedRealSpaceModes.dat
RealSpaceModesOn.dat
H0RealSpace.txt
The folder Init_Electr_Modes/Wannier-Stark_States/
shows the eigenstates of the Schrödinger equation. In this folder, a default potential drop per period is taken as 1/2 of the <Energy_Range_Axial> specified in the input file. Otherwise it can be specified in the input file using the command <Bias_for_initial_Electronic_Modes>
in the <Simulation_Parameter>
section.
It contains:
Effective_masses.dat
Miniband #
Effective mass in the well [m0]
Effective mass in the barrier [m0]
Wannier-Stark_Energy_Separation.dat
Wannier-Stark_levels.dat
This file contains the conduction band edge and the probability densities.Wannier-Stark_levelsOn.dat
This file contains the conduction band edge and the probability densities. Points where the probability density is almost zero are omitted.
The Tight-binding folder contains data only if one or several <Analysis_Separator>
are defined in the input file. The tight-binding basis corresponds to piecewise solution of the Schrödinger equation between these separators.
The file Lateral_spectrum.dat
gives the energy discretization for the states used to describe the 2-Dimensional (2D) motion in the directions (x,y) perpendicular to the heterostructure. The lateral motion is discretized using cylindrical boundary conditions, and the corresponding eigenstates are Bessel funcitons.
$x$ axis: Lateral state index
$y$ axis: order of Bessel
(zero index)-1 of Bessel
Relative Energy (meV)
.
For each voltage or temperature step, the following files are produced as a result of the NEGF calculation:
CarrierDensity.dat
Conduction_BandEdge.dat
Convergence.txt
NO-CONVERGENCE.txt
CurrentDensity.dat
Current-miscellaneous.txt
Electrostatic-Potential.dat
3 folders are created to output physical quantities in 3 different basis set (reduced real space, Wannier-Stark, and Tight-binding).
WannierStark_Energy_Separation.dat
EnergySpacing.dat
for a particular voltage.Wannier-Stark_levels.dat
EnergyLevel_Absolute.dat
for a particular voltage.)Wannier-Stark_levelsOn.dat
The folder 2D_Plots_Position-nm_Energy-eV/
contains files where the $x$ axis is position in [nm] and the $y$ axis is energy in units of [eV].
Note that these 2D plots show 2 QCL periods although only 1 period is simulated.
DOS.fld
/ *.coord
/ *.dat
Carrier_Density.fld
/ *.coord
/ *.dat
Current_Density.fld
/ *.coord
/ *.dat
The folder Gain/
contains files where the $x$ axis is position in [nm] and the $y$ axis is photon energy $E_{\rm ph}$ in units of [eV].
Note that these 2D plots show 2 QCL periods although only 1 period is simulated.
Energy-Resolved_Gain_Simple-Approximation.fld
/ *.coord
/ *.dat
Gain_Simple-Approximation.dat
Gain_SelfConsistent.dat
A negative value of gain corresponds to absorption.
Note that the gain output is only done for the voltages specified in the input file.
<!-- Calculate gain only between the following values of potential drop per period in order to save CPU time --> <Vmin unit="mV"> 160 </Vmin> <Vmax unit="mV"> 400 </Vmax>
The folder GreenFunctions/
contains information on the Green's functions.
The electron density $n(x,E_x)$ is related to the lesser Green's function $\mathbf{G}^<$ (“G lesser”): $$n(x,E_x) = - \frac{{\rm i}}{2\pi} \mathbf{G}(x,x^\prime=x,E_x)$$
GreenLesser_All.dat
GreenLesser_Z.dat
The local density of states $\rho(x,E_x)$ is related to the spectral function $\mathbf{A}$: $$\rho(x,E_x) = \frac{1}{2\pi} \mathbf{A}(x,x^\prime=x,E_x)$$ $\mathbf{A}$ is defined as $\mathbf{A} = {\rm i} (\mathbf{G}^{\rm R} - \mathbf{G}^{{\rm R}\dagger}) = - 2 {\rm Im}(\mathbf{G}^{\rm R})$. $\mathbf{G}^{\rm R}$ is the retarded Green's function.
GreenSpectral_All.dat
<Emin_shift unit="meV">
can be increased (by 200 meV) to reduce the calculation time. Essentially, the energy range of the Green's functions is altered by adjusting <Emin_shift unit=meV>
and <Emax_shift unit=meV>
.GreenSpectral_Z.dat
The folder DensityMatrix/
contains the density matrix $\rho$ which is a complex quantity and it is dimensionless.
The trace of the density matrix equals 1.
In our case, the trace is 1 if we sum over one period.
The state labels (state $i$, period $j$) are specified in the complex density matrix.
$$\rho(i,j) = \rho({\rm state},{\rm period})$$
DensityMatrix_complex.mat
DensityMatrix_RealPart_AbsoluteValue.mat
DensityMatrix_ImaginaryPart_AbsoluteValue.mat
For each simulation, the following files are produced.
Energy_WannierStarkStates.dat
Gain_vs_Voltage.dat
and Gain_vs_EField.dat
Current_vs_Voltage.dat
and Current_vs_EField.dat
Current-Density.dat
.