nextnano³ - Tutorial

next generation 3D nano device simulator

last updated: 25-01-10

Author: Stefan Birner
Please send comments to nextnano3 (-at-) wsi.tum.de.

This is a general introduction in how to make your first steps with the 3D Nano Device Simulation program and to get acquainted with the basics.

Check out the Overview section and browse through it to get an idea what it is all about.

First of all it would be advisable to have a brief look at the structure of the code and how the input data will be processed.

• Structure of the program

If you encounter any technical terms that you are unfamiliar with, please check the glossary. If you cannot find an answer or if you find that the tutorial in general lacks some information or if it is totally confusing, please let us know and we will try to update it to your needs.

The physics is explained in the section Basics. You can download a pdf-file and print out an old version of the Basics (partly in German, won't be updated any more) here. First, the underlying physical equations are introduced and discussed, followed by remarks to the general program flow and technical details of the quantum regions. Eventually, the internal program flow will be described mainly with respect to the quantum states. A further chapter is devoted to multiband kp theory, including the description of the definiton of the Hamiltonian as it is used in the program.

General information on the simulation program and how to make it run

The geometry of the device is completely specified in the input file. This is the file that the user should edit in general. The name of this input file must be written into the second line of the file keywords.in. Apart from this modification keywords.in must not be changed.

The parameters of the materials will be read in via the database database.in. This is the place where you can change material data in case you want to.

Additional information for the keywords and the database can be found here:

• Keywords - important for your input file
• Database - important if you want to change/add some parameters, e.g. see also section How to input material parameters.
• Input parser - general manual on how the input/output system works

Four example files are provided  (input_file1.in, input_file2.in, input_file3.in, input_file4.in) in Tutorial 1 which represent typical simulation settings that are connected to each other. These files contain extensive comments to guide you through your first experience with the input system.

(Further details on the definitions of the input keywords can be found in the script input_parser_docu.doc which can be printed out. Again, this file won't be updated any more and therefore we suggest to consult the sections Input parser, Keywords and Database instead. Brief comments can also be found in keywords.in itself.)

The output of the data is also controlled by the input file. Explanations can be found in the example files. More information on the output of the data is also contained in the section Keywords.

The program is still in the phase of development implying that there will always be aspects that could be considered additionally or described differently. If you have further comments or suggestions you are welcome to contact nextnano3@wsi.tum.de.

Now it's time to get started...

1D Tutorials

• Simple SiGe structure
  Step 1: Simple SiGe structure
  Step 2: Include current
  Step 3: Include quantum models (1-band Schrödinger equation)
  Step 4: Read in data and solve k.p
• Electron concentration in doped semiconductors (Si, Ge, GaAs) - Compensated semiconductors
• Tight-binding band structure of bulk materials (Empirical tight-binding (sp³s*) band structure of GaAs, GaP and AlAs)
• Tight-binding band structure of graphene
• Carrier statistics of graphene sheets
• Poisson equation (for different charge density profiles)
• Triangular well
• Parabolic quantum well
• Double quantum well
• Electron density of states (DOS) of a GaAs quantum well and
  hole density of states (DOS) of a Si hole channel
• Quantum Confined Stark Effect
• Exciton correction in 1D quantum wells
• Quantum Cascade Laser
• Intraband transitions
• Interband transitions
• Intersubband transitions in InGaAs/AlInAs multiple quantum well systems
• Scattering times for electrons in unbiased and biased single and multiple quantum wells
• Schottky barrier
• Schrödinger-Poisson
• pn-junction
• Transmission function - NEGF
• Ballistic current in a resonant tunneling diode (RTD)
• inverted High Electron Mobility Transistor (HEMT)
• FET - Field Effect Transistor
  - How to incorporate voltage sweep steps
• Quantum well structure
  - Piezoelectric fields and strain
• Piezoelectric field in InAs/GaAs QWs grown along the [111] orientation
• HEMT structure (high electron mobility transistor)
• Strained AlAs QW - Crossover of ground states
• k_|| dispersion of holes in a GaAs/AlAs quantum well
  -> How to modify database parameters in the input file.
• Strain: Band shifts and splittings due to conduction and valence band deformation potentials
• Band gap of strained AlGaInP on GaAs substrate
• Strain and displacement tensors along different growth directions
• Growth of layers on strained (or stressed) substrates (biaxial and uniaxial)
• GaN/AlN wurtzite structure: Strain, piezo and pyroelectric charges in wurtzite
• Optical absorption of an InGaAs quantum well
• k.p dispersion in bulk GaAs (strained / unstrained)
• k.p dispersion in bulk GaN (wurtzite) (strained / unstrained)
• k.p dispersion in bulk unstrained ZnS, CdS and CdSe (wurtzite)
• k_|| dispersion of holes in a GaN/AlGaN quantum well
• p-Si / SiO₂ / poly-Si structure (MOSFET with inversion channel due to applied gate voltage)
• Capacitance-Voltage (C-V) curve of a "metal"-insulator-semiconductor (MIS) structure
• strained silicon
• Si/SiGe MODQW (Modulation Doped Quantum Well)
• k_|| dispersion of holes in unstrained and strained silicon inversion layers
• Self-consistent 6x6 k.p calculations of holes in strained Si/SiGe MOSFETs
• Dispersion in infinite superlattices: Minibands
• InAs / In_0.4Ga_0.6Sb superlattice dispersion with 8x8 k.p (type-II band alignment)
• InAs / GaSb broken gap quantum well (BGQW) (type-II band alignment)
• Single-band ('effective-mass') is a special case of 8x8 k.p ('8x8kp') if the electrons are decoupled from the holes
  Self-consistent calculation of the quantum mechanical density within the single-band approximation and 8x8 k.p
  Calculation of the quantum mechanical density from the k.p dispersion (no self-consistency)
• Electron density in doped semiconductors
• Resistance in bulk n-type doped silicon
• n-i-n Si resistor (classical and quantum mechanical current calculation)
• Mobility in two-dimensional electron gases (2DEGs) - InSb, GaAs and InGaAs quantum wells
• Cascade solar cell (AlGaAs/InGaAs tandem solar cell)

1D BIO-nextnano³

   ISFET (Ion-Sensitive Field Effect Transistor)

• Poisson-Boltzmann equation: The Gouy-Chapman solution
• Extended Poisson-Boltzmann equation: Potentials of mean force (PMF)
• Electrolyte Gate AlGaN/GaN Field Effect Transistor as pH Sensor
• Si-SiO₂ electrolyte sensor
• Detection of proteins with a SOI (silicon-on-insulator) electrolyte sensor

2D Tutorials

• Quantum corral
• Energy dispersion of a cylindrically shaped GaN nanowire
• DGMOS - Double Gate MOSFET (Metal Oxide Semiconductor Field Effect Transistor)
• DGMOS - Double Gate MOSFET (quantum mechanical calculation)
• Electron wavefunctions of a 2D slice of a Triple Gate MOSFET
• Quantum wire
• - I-V curve of an n-doped Si structure
  - I-V curve of an n-i-n-doped Si structure
• 2D Tutorial of the 1D tutorial:
  Single-band ('effective-mass') is a special case of 8x8 k.p ('8x8kp') if the electrons are decoupled from the holes
  Calculating the quantum mechanical density within the single-band approximation and 8x8 k.p self-consistently
  Calculation of the quantum mechanical density from the k.p dispersion (no self-consistency)
• Electron and hole wavefunctions in a T-shaped quantum wire grown by CEO (cleaved edge overgrowth)
• Electron and hole wavefunctions in a strained T-shaped quantum wire grown by CEO (cleaved edge overgrowth)
• Exciton correction in 2D quantum wires
• Landau levels in bulk GaAs (magnetic field)
• Fock-Darwin states of a 2D parabolic potential (magnetic field)
• Fock-Darwin states of a 2D parabolic, anisotropic (elliptical) potential in a magnetic field
• Vertically coupled quantum wires in a longitudinal magnetic field
• Efficient method for the calculation of ballistic quantum transport - The CBR method (2D example)

3D Tutorials

• Artificial atom
• Artificial atom - Si QD with 6x6 k.p
• Cubic and cuboidal shaped quantum dots
• Artificial quantum dot crystal - Superlattice dispersion (minibands)
• Intermediate-band solar cell (artificial quantum dot crystal)
• InGaAs quantum dot grown on GaAs substrate
• Energy levels in a pyramidal shaped InAs/GaAs quantum dot including strain and piezoelectric fields
• Hexagonal shaped GaN quantum dot embedded in AlN (wurtzite)
• QD molecule
• Exciton and biexciton correction in idealistic 3D cubic quantum dots
• Nanocrystals
• Cleaved edge overgrowth quantum dots (CEO QDs)
• Single-electron transistor
• Strain effects in freestanding three-dimensional nitride nanostructures
• Transmission through a 3D nanowire

Have fun!

The nextnano³ source code and executable (Windows PC only) can be downloaded from the Download section. Check the News section for changes in the code and if you are interested in updating single files you can get the source from the folder  nextnano3/restricted/source_code/[subfolder]/filename.f90.
See Download section for details.

• Please help us to improve our tutorial. Send comments to nextnano3 (-at-) wsi.tum.de.