
Band Structure Lab Exercise
28 Jun 2010  Teaching Materials  Contributor(s): Gerhard Klimeck, Parijat Sengupta, Dragica Vasileska
Investigations of the electron energy spectra of solids form one of the most active fields of research. Knowledge of band theory is essential for application to specific problems such as Gunn diodes, tunnel diodes, photodetectors etc. There are several standard methods to compute the band structure of solids and confined devices (such as wells, wires, and dots) carved out of them. We will use the Band structure lab to generate the band diagrams of several materials and devices. A full list of …

Crystal Viewer Lab Exercise
28 Jun 2010  Teaching Materials  Contributor(s): Gerhard Klimeck, Parijat Sengupta, Dragica Vasileska
A central problem in the investigation of material properties involves the examination of the underlying blocks that aggregate to form macroscopic bodies. These underlying blocs own a definite arrangement that is repeated in three dimensions to give the crystal structure. We will try to explore the geometry of some well known class of materials (e.g., diamond, zincblende, wurtzite etc,) and learn techniques of identifying planes (Miller indices) and directions in these crystal structures. …

Negative Differential Resistivity Exercise
28 Jun 2010  Teaching Materials  Contributor(s): Gerhard Klimeck, Parijat Sengupta, Dragica Vasileska
In certain semiconductors such as GaAs and InP the average velocity as a function of field strength displays a maximum followed by a regime of decreasing velocity. Hilsum, Ridley, and Watkins postulated that peculiarities in the band structure of semiconductors would lead to the above phenomenon. The conduction band in compound semiconductors such as GaAs has away from the Г point (centre of Brillouin zone) local minima at the X and L valleys (satellite valleys). These valleys are a few …

Exercise for MOSFET Lab: Device Scaling
28 Jun 2010  Teaching Materials  Contributor(s): Dragica Vasileska, Gerhard Klimeck
This exercise explores device scaling and how well devices are designed.

PieceWise Constant Potential Barrier Tool MATLAB Code
19 Jun 2010  Downloads  Contributor(s): Dragica Vasileska, Gerhard Klimeck
this is the MATLAB code of the PCPBT in the effective mass approximation.

Quantum Bound States Exercise
16 Jun 2010  Teaching Materials  Contributor(s): Gerhard Klimeck, Parijat Sengupta, Dragica Vasileska
Exercise Background
Quantummechanical systems (structures, devices) can be separated into open systems and closed systems. Open systems are characterized with propagating or current carrying states. Closed (or bound) systems are described with localized wavefunctions. One such system is a triangular potential well in MOS capacitors; another one is rectangular quantum well in heterostructure devices. In addition to this, every observable in Quantum Mechanics (like position, momentum, energy) …

Quantum Tunneling Exercise
16 Jun 2010  Teaching Materials  Contributor(s): Gerhard Klimeck, Parijat Sengupta, Dragica Vasileska
Exercise Background
Tunneling is fully quantummechanical effect that does not have classical analog. Tunneling has revolutionized surface science by its utilization in scanning tunneling microscopes. In some device applications tunneling is required for the operation of the device (Resonant tunneling diodes, EEPROMs â�� floating gate memories), but in some cases it leads to unwanted power dissipation, such as gate leakage in both MOS and Schottky transistors.
Exercise Objectives
The …

Periodic Potentials Exercise
16 Jun 2010  Teaching Materials  Contributor(s): Gerhard Klimeck, Parijat Sengupta, Dragica Vasileska
In this exercise, various calculations of the electronic band structure of a onedimensional crystal are performed with the KronigPenney (KP) model. This model has an analytical solution and therefore allows for simple calculations. More realistic models always require extensive numeric calculations, often on the fastest computers available. The electronic band structure is directly related to many macroscopic properties of the material and therefore of large interest. Nowadays, hypothetical …

Crystal Viewer Tool Verification (V 2.3.4)
15 Jun 2010  Teaching Materials  Contributor(s): Dragica Vasileska, Gerhard Klimeck
This text verifies the Crystal Viewer Tool by comparing the amount of dangling bonds at the silicon surface for [100], [110] and [111] crystal orientation. The crystal viewer results are in agreement with experimental findings.

Crystal Structures  Packing Efficiency Exercise
15 Jun 2010  Teaching Materials  Contributor(s): Dragica Vasileska, Gerhard Klimeck
Consider the most efficient way of packing together equalsized spheres and stacking closepacked atomic planes in three dimensions. For example, if plane A lies beneath plane B, there are two possible ways of placing an additional atom on top of layer B. If an additional layer was placed directly over plane A, this would give rise to the following series :
...ABABABAB....
This type of crystal structure is known as hexagonal close packing (hcp).
If however, all three planes are staggered …

PCPBT Manual
08 Jun 2010  Teaching Materials  Contributor(s): Dragica Vasileska, Gerhard Klimeck
This is a manual for the PieceWise Constant Potential Barrier Tool.

TightBinding Band Structure Calculation Method
08 Jun 2010  Teaching Materials  Contributor(s): Dragica Vasileska, Gerhard Klimeck
This set of slides describes on simple example of a 1D lattice, the basic idea behind the TightBinding Method for band structure calculation.

Crystal Structures
08 Jun 2010  Teaching Materials  Contributor(s): David K. Ferry, Dragica Vasileska, Gerhard Klimeck
In mineralogy and crystallography, a crystal structure is a unique arrangement of atoms in a crystal. A crystal structure is composed of a basis, a set of atoms arranged in a particular way, and a lattice. The basis is located upon the points of a lattice spanned by lattice vectors, which is an array of points repeated periodically in three dimensions. The set of points forming a volume that can completely fill the space of the lattice when translated by integral multiples of the lattice …

Crystal Directions and Miller Indices
08 Jun 2010  Teaching Materials  Contributor(s): David K. Ferry, Dragica Vasileska, Gerhard Klimeck
Miller indices are a notation system in crystallography for planes and directions in crystal lattices. In particular, a family of lattice planes is determined by three integers, l, m, and n, the Miller indices. They are written (lmn) and denote planes orthogonal to a direction (l,m,n) in the basis of the reciprocal lattice vectors.

Verification of the Validity of the PN Junction Tool
08 Jun 2010  Teaching Materials  Contributor(s): Dragica Vasileska, Gerhard Klimeck
These simulations and comparisons with the depletion charge approximation prove the validity of the PN Junction tool.

Solve a Challenge for a PN Diode
08 Jun 2010  Teaching Materials  Contributor(s): Dragica Vasileska, Gerhard Klimeck
This is SOLVE A CHALLENGE PROBLEM for pndiodes.

Worked Examples for a PN Diode
01 Jun 2010  Teaching Materials  Contributor(s): Dragica Vasileska, Gerhard Klimeck
several worked examples are presented that illustrate the operation of a PN diode.

InAs: Evolution of isoenergy surfaces for heavy, light, and splitoff holes due to uniaxial strain.
25 May 2010  Animations  Contributor(s): Abhijeet Paul, Denis Areshkin, Gerhard Klimeck
Movie was generated using Band Structure Lab tool at nanoHUB and allows to scan over four parameters:
Hole energy measured from the top of the corresponding band (i.e. the origin of energy scales for LH and SOH is different)
Strain direction: [001], [110], [111]
Carrier type: LH, HH, SOH
Strain value
Red lines indicate reciprocal halfvectors in [111] directions (Lpoints in Brillouin zone).
Scan proceeds as four nested cycles for the variables listed from left to right, i.e. the …

Carbon nanotube bandstructure
22 Apr 2010  Animations  Contributor(s): Saumitra Raj Mehrotra, Gerhard Klimeck
Carbon nanotubes are allotropes of carbon with a cylindrical nanostructure, and can be categorized into singlewalled nanotubes (SWNT) and multiwalled nanotubes (MWNT). These cylindrical carbon molecules have novel properties that make them potentially useful in many nanotechnology applications, including electronics, optics and other fields of materials science.
Because of its unique symmetry the structure of a singlewalled nanotube will strongly affect its electrical properties. For a …

Threshold voltage in a nanowire MOSFET
22 Apr 2010  Animations  Contributor(s): Saumitra Raj Mehrotra, SungGeun Kim, Gerhard Klimeck
Threshold voltage in a metal oxide semiconductor fieldeffect transistor (better known as a MOSFET) is usually defined as the gate voltage at which an inversion layer forms at the interface between the insulating layer (oxide) and the substrate (body) of the transistor. A MOSFET is said to be turned ON or be in the ON state beyond the threshold voltage.
With the scaling of MOSFET channel lengths, researchers are looking at new transistor designs. Among them is the gateallaround nanowire …

Resonant Tunneling Diode operation
22 Apr 2010  Animations  Contributor(s): Saumitra Raj Mehrotra, Gerhard Klimeck
A resonant tunneling diode (RTD) is a type of diode with a resonant tunneling structure that allows electrons to tunnel through various resonant states at certain energy levels. RTDs can be fabricated using many different types of materials (such as IIIV, type IV, IIVI semiconductors) and different types of resonant tunneling structures (such as heavily doped pn junction in Esaki diodes, double barriers, triple barriers, quantum wells, quantum wires or quantum dots). …

Nanotechnology Animation Gallery
22 Apr 2010  Teaching Materials  Contributor(s): Saumitra Raj Mehrotra, Gerhard Klimeck
Animations and visualization are generated with various nanoHUB.org tools to enable insight into nanotechnology and nanoscience. Click on image for detailed description and larger image download. Additional animations are also available
Featured nanoHUB tools:
Band Structure Lab.
Carrier Statistics Lab
CNTBands
Crystal Viewer
DriftDiffusion Lab
MOSCap
OMEN Nanowire
PN …

CV profile with different oxide thickness
20 Apr 2010  Animations  Contributor(s): Saumitra Raj Mehrotra, Gerhard Klimeck
CV (or capacitancevoltage) profiling refers to a technique used for the characterization of semiconductor materials and devices. CV testing is often used during the characterization process to determine semiconductor parameters, particularly in MOSCAP and MOSFET structures.
CV measurements can reveal oxide thickness, oxide charges, contamination from mobile ions, and interface trap density in wafer processes. In this image the CV profile for a bulk ptype substrate MOSCAP with different …

PN junction in forward bias
17 Apr 2010  Animations  Contributor(s): Saumitra Raj Mehrotra, Gerhard Klimeck
A PN junction is formed by joining ptype and ntype doped semiconductors together in very close contact. The p and ntype semiconductors are conducting because of the available free carriers. However, because the carriers diffuse into the adjoining p and n regions by a process called recombination the contact region is nonconducting. This region is called depletion region.
The application of a positive bias on the ptype end will lead a PN junction into the forward biased mode of …

Local density of states
17 Apr 2010  Animations  Contributor(s): Saumitra Raj Mehrotra, Gerhard Klimeck
The concept of general density of states (DOS) in devices is, by definition, spatially invariant. However, in the case of inhomogeneous materials or in quantum confined structures, the density of states can be resolved in space. This is known as local density of states, or LDOS. …