# 5. Workshop¶

A few next**nano** workshops were held in the past using the material presented below.
The following tutorials are suited to learn more about the next**nano** software.

Schrödinger-Poisson - A comparison to the tutorial file of Greg Snider’s code

Optical interband transitions in a quantum well - Matrix elements and selection rules

Two-dimensional electron gas in an AlGaN/GaN field effect transistor

\(\mathbf{k} \cdot \mathbf{p}\) dispersion in bulk GaAs (strained / unstrained)

\(\mathbf{k} \cdot \mathbf{p}\) dispersion in bulk unstrained ZnS, CdS, CdSe and ZnO (wurtzite)

\(\mathbf{k} \cdot \mathbf{p}\) energy dispersion of holes in a quantum well

Capacitance-Voltage curve of a metal–insulator–semiconductor (MIS) structure

Energy levels in a pyramidal shaped InAs/GaAs quantum dot including strain and piezoelectric fields

## 5.1. pn junction¶

*recommended*

https://www.nextnano.com/nextnano3/tutorial/1Dtutorial_pn_junction.htm

`pn_junction_GaAs_1D*.in`

(next**nano**++ & next

**nano**³)

`pn_junction_GaAs_2D*.in`

(next**nano**++ & next

**nano**³)

- Summary
This example is rather simple.

- Model used
1D; Poisson equation

- Task
Try to reproduce the results in the figures. Run and plot the 2D files.

- Challenge
To plot two different graphs, i.e. data files, simultaneously. Export the graph containing two different graphs to gnuplot. Export a 2D file to gnuplot.

- Duration
10 minutes

## 5.2. Double Quantum Well¶

*recommended*

`DoubleQuantumWell_*.in`

(next**nano**++ & next

**nano**³)

- Summary
This example teaches quantum physics: bonding and anti-bonding wavefunctions.

- Model used
1D; Schrödinger equation

- Task
Try to reproduce the results in the figures.

- Challenge
Perform a parameter sweep using next

**nano**mat ’s Template feature and do a post-processing using next**nano**mat to reproduce the figure*Eigenvalues vs. barrier width*. Export the graph to gnuplot.- Duration
20 minutes

## 5.3. Multiple quantum wells and finite superlattices¶

`Superlattice_N_wells_nnp.in`

(next**nano**++)

- Summary
Covers sweeping variables. The transition between a finite superlattice and a multiple quantum well system is observed by changing the number of wells in the system.

- Model used
1D; Schrödinger-Poisson

- Task
Try to reproduce the structure of the system and the results in the figures

- Challenge
Perform a parameter sweep with next

**nano**mat or next**nano**py. If the latter is chosen, perform post-processing using next**nano**py to match Harrison’s figures.- Duration
30 minutes

## 5.4. Schrödinger-Poisson - A comparison to the tutorial file of Greg Snider’s code¶

*recommended*

`Greg_Snider_MANUAL_*.in`

(next**nano**++ & next

**nano**³)

- Summary
This example is relatively easy.

- Model used
1D; self-consistent Schrödinger-Poisson

- Task
Try to reproduce the results in the figures.

- Challenge
To plot two different graphs, i.e. data files, simultaneously. Understand where you find eigenvalues and wavefunctions. Export the graph containing two different graphs to gnuplot.

- Duration
20 minutes

## 5.5. InGaAs Multi-Quantum Well Laser diode¶

*very important*

`LaserDiode_InGaAs_1D_cl_nnp.in`

(next**nano**++)

`LaserDiode_InGaAs_1D_qm_nnp.in`

(next**nano**++)

- Summary
This example teaches how to apply a bias and solve the coupled system of Schrödinger, Poisson and Current equations.

- Model used
1D; selfconsistent Schrödinger–Poisson–current

- Task
Try to reproduce some of the figures.

- Challenge
To understand how a laser works. Plot the recombination rates and the classical emission spectrum. Do a parameter sweep, e.g. number of wells, doping, alloy content and see how the classical emission spectrum changes. Plot the wavefunctions. Compare the classical density vs. the quantum density for the same bias, e.g. for 1 V where the quantum wells contain a significant density. Plot the convergence log files on a logarithmic scale. Plot the current densities, IV curve, doping profile, …

- Duration
40 minutes

## 5.6. Optical interband transitions in a quantum well - Matrix elements and selection rules¶

*optional*

https://www.nextnano.com/nextnano3/tutorial/1Dtutorial_OpticalTransitions.htm

`1DQW_interband_matrixelements_*.in`

(next**nano**++ & next

**nano**³)

- Summary
This example teaches how to calculate the spatial overlap of electron and hole wavefunctions and their transition energy.

- Model used
1D; Schrödinger equation

- Task
Try to reproduce the results in the figures.

- Challenge
Compare the infinite vs. finite quantum well to understand selection rules.

- Duration
10 minutes

## 5.7. Wurtzite¶

*optional*

https://www.nextnano.com/nextnano3/tutorial/1Dtutorial11.htm

`wurtzite*.in`

(next**nano**++ & next

**nano**³)

- Summary
This example is relatively easy and discusses strain, piezo any pyroelectricity.

- Model used
1D; strain and Poisson equation

- Task
Try to reproduce the results in the figures.

- Challenge
To understand the peculiarities of wurtzite.

- Duration
20 minutes

## 5.8. Two-dimensional electron gas in an AlGaN/GaN field effect transistor¶

*optional*

https://www.nextnano.com/nextnano3/tutorial/1Dtutorial_AlGaN_GaN_FET.htm

`Jogai_AlGaNGaN_FET_JAP2003*.in`

(next**nano**++ & next

**nano**³)

- Summary
This example is nice. Try to reproduce some of the figures.

- Model used
1D; strain, selfconsistent Schrödinger–Poisson

- Task
Try to reproduce the results in the figures.

- Challenge
Can you do a parameter sweep using next

**nano**mat ’s Template feature and plot the 2DEG density vs. \(\text{Al}_x\text{Ga}_{1-x}\text{N}\) thickness?- Duration
20 minutes

## 5.9. \(\mathbf{k} \cdot \mathbf{p}\) dispersion in bulk GaAs (strained / unstrained)¶

*advanced*

https://www.nextnano.com/nextnano3/tutorial/1Dtutorial13.htm

`bulk_kp_dispersion_GaAs*.in`

(next**nano**++ & next

**nano**³)

- Summary
This example teaches the \(\mathbf{k} \cdot \mathbf{p}\) band structure.

- Model used
bulk; strain, \(\mathbf{k} \cdot \mathbf{p}\)

- Task
Try to reproduce some of the figures: Plot the single-band, the 6-band dispersion and the 8-band \(E(k)\) dispersion in the same plot. Do the same for the strained case to see how strain alters the band structure.

- Challenge
To understand the \(\mathbf{k} \cdot \mathbf{p}\) method.

- Duration
15 minutes

## 5.10. \(\mathbf{k} \cdot \mathbf{p}\) dispersion in bulk unstrained ZnS, CdS, CdSe and ZnO (wurtzite)¶

*advanced*

https://www.nextnano.com/nextnano3/tutorial/1Dtutorial_bulk_6x6kp_dispersion_IIVI.htm

`bulk_6x6kp_dispersion_ZnO*.in`

(next**nano**++ & next

**nano**³)

- Summary
This example teaches the \(\mathbf{k} \cdot \mathbf{p}\) valence band structure for wurtzite materials.

- Model used
bulk; strain, \(\mathbf{k} \cdot \mathbf{p}\)

- Task
Try to reproduce some of the figures.

- Challenge
To understand the \(\mathbf{k} \cdot \mathbf{p}\) method for wurtzite.

- Duration
5 minutes

## 5.11. \(\mathbf{k} \cdot \mathbf{p}\) dispersion in bulk unstrained, compressively and tensilely strained GaN (wurtzite)¶

*advanced*

https://www.nextnano.com/nextnano3/tutorial/1Dtutorial_strained_GaN_dispersion.htm

`bulk_kp_dispersion_GaN_unstrained*.in`

(next**nano**³)

- Summary
This example teaches the \(\mathbf{k} \cdot \mathbf{p}\) valence band structure for wurtzite materials.

- Model used
bulk; strain, \(\mathbf{k} \cdot \mathbf{p}\)

- Task
Try to reproduce some of the figures.

- Challenge
To understand the \(\mathbf{k} \cdot \mathbf{p}\) method for wurtzite.

- Duration
10 minutes

## 5.12. \(\mathbf{k} \cdot \mathbf{p}\) energy dispersion of holes in a quantum well¶

*advanced*

https://www.nextnano.com/nextnano3/tutorial/1Dtutorial8.htm

`1Dwell_GaAs_AlAs_*.in`

(next**nano**++ & next

**nano**³)

- Summary
This example teaches the \(\mathbf{k} \cdot \mathbf{p}\) model: \(E\left(k_{\parallel}\right)\) dispersion.

- Model used
1D; \(\mathbf{k} \cdot \mathbf{p}\) Schrödinger equation

- Task
Try to reproduce some of the figures.

- Challenge
To understand the \(\mathbf{k} \cdot \mathbf{p}\) features for heterostructures.

- Duration
20 minutes

## 5.13. \(\mathbf{k} \cdot \mathbf{p}\) energy dispersion of an unstrained GaN QW embedded between strained AlGaN layers¶

*advanced*

https://www.nextnano.com/nextnano3/tutorial/1Dtutorial_GaN_AlGaN_QW_dispersion.htm

`1DGaN_AlGaN_QW_k_zero_*.in`

(next**nano**++ & next

**nano**³)

- Summary
This example teaches the \(\mathbf{k} \cdot \mathbf{p}\) model: \(E\left(k_{\parallel}\right)\) dispersion.

- Model used
1D; \(\mathbf{k} \cdot \mathbf{p}\) Schrödinger equation

- Task
Try to reproduce some of the figures.

- Challenge
To understand the \(\mathbf{k} \cdot \mathbf{p}\) features for heterostructures.

- Duration
20 minutes

## 5.14. Capacitance-Voltage curve of a metal–insulator–semiconductor (MIS) structure¶

*advanced*

https://www.nextnano.com/nextnano3/tutorial/1Dtutorial_MIS_CV.htm

`1DMIS_CV_Fermi_*.in`

(next**nano**++ & next

**nano**³)

- Summary
This example teaches how to apply a bias without solving the current equation.

- Model used
1D; selfconsistent Schrödinger–Poisson

- Task
Try to reproduce some of the figures.

- Challenge
To understand how to integrate charge carrier densities in specific regions.

- Duration
20 minutes

## 5.15. Core-shell nanowire¶

*recommended*

Schrödinger equation of a two-dimensional core-shell structure

Hexagonal 2DEG - Two-dimensional electron gas in a delta-doped hexagonal shaped GaAs/AlGaAs nanowire heterostructure

https://www.nextnano.com/nextnano3/tutorial/2Dtutorial_core_shell_circle_hexagon.htm

`2DGaAs_AlGaAs_*.in`

(next**nano**++ & next

**nano**³)

`2D_Hexagonal_Nanowire_2DEG*.in`

(next**nano**++ & next

**nano**³)

- Summary
This example teaches how to perform a 2D simulation.

- Model used
2D; Schrödinger equation, selfconsistent Schrödinger–Poisson

- Task
Try to reproduce some of the figures.

- Challenge
To understand how to visualize 2D results and how to export them to gnuplot. Plot the geometry together with the electron density of the modulation doped core-shell nanowire in one graph.

- Duration
15 minutes

## 5.16. Quantum dot molecule¶

*advanced*

`3DQD_molecule_cuboid_asymmetric_*.in`

(next**nano**++ & next

**nano**³)

- Summary
This example teaches how to apply an electric field in a 3D simulation.

- Model used
3D; Schrödinger equation

- Task
Try to reproduce some of the figures.

- Challenge
To understand how to visualize 3D results and how to export them to Paraview.

- Duration
10 minutes

## 5.17. Energy levels in a pyramidal shaped InAs/GaAs quantum dot including strain and piezoelectric fields¶

*advanced*

https://www.nextnano.com/nextnano3/tutorial/3Dtutorial_QD_pyramid.htm

`3DInAsGaAsQDPyramid_PryorPRB1998_10nm_*.in`

(next**nano**++ & next

**nano**³)

- Summary
This example teaches how to calculate and plot strain, piezoelectric charge densities and wavefunctions in a 3D simulation.

- Model used
3D; strain equation, Poisson equation, Schrödinger equation

- Task
Try to reproduce some of the figures.

- Challenge
To understand how to visualize 3D results and how to export them to Paraview.

- Duration
20 minutes

## 5.18. Single-electron transistor - laterally defined quantum dot¶

*advanced*

https://www.nextnano.com/nextnano3/tutorial/3Dtutorial_SET_lateral_QD.htm

`SET_Scholze_IEEE2000_*.in`

(next**nano**++ & next

**nano**³)

- Summary
This example teaches how a gate geometry depletes the 2DEG density locally.

- Model used
1D, 3D; Poisson equation, Schrödinger equation, selfconsistent Schrödinger–Poisson

- Task
Try to reproduce some of the figures.

- Challenge
To understand how to visualize 3D results and how to export them to Paraview.

- Duration
15 minutes

Note

Search through

the other input files in the installation folder,

the list of tutorials on the website, https://www.nextnano.com/nextnano3/tutorial/tutorial.htm

and simulate the topics that are of interest for you.

Important next**nano**mat features that you should learn

Tree View vs. List View

Parameter sweeps using Template

Parameter sweep post-processing using Template

Postprocessing using next

**nano**pyMulti-Parameter sweeps using Template (beta)

Batch list

Exporting 2D slices of 3D data

Exporting 1D slices of 2D/3D data

Export to

`.vtr`

Exporting 3D data to Paraview

Open files with notepad++, Origin, …

Plotting several graphs (Overlay)

Plotting several graphs in 2D/3D (Overlay)

Zoom feature

`SOFT_KILL`

featureDisplay options

Tools Options

HTCondor Cloud Computing

In principle you can run also you own software with next

**nano**mat. next**nano**mat can run**any**executable either locally or on HTCondor.How to access online documentation and how it is structured.

Which features are you missing?

If you have any comments or suggestions regarding this workshop material, please send your feedback to `support [at] nextnano.com`

.
We really appreciate your feedback on errors, broken links, typos, …