
Solar Cells Operation and Modeling
19 Jul 2010  Teaching Materials  Contributor(s): Dragica Vasileska, Gerhard Klimeck
This set of slides decribes the basic principles of operation of various generations on solar cells with emphasis to single crystalline solar cells. Next, semiconductor equations that describe the operation of a solar cell under simplified conditions is given. Finally, modeling of single junction solar cells is described. Modeling of solar cells with Silvaco simulation software is also outlined.
NSF

Atomistic Simulations of Reliability
06 Jul 2010  Teaching Materials  Contributor(s): Dragica Vasileska
Discrete impurity effects in terms of their statistical variations in number and position in the inversion and depletion region of a MOSFET, as the gate length is aggressively scaled, have recently been researched as a major cause of reliability degradation observed in intradie and dietodie threshold voltage variation on the same chip resulting in significant variation in saturation drive (on) current and transconductance degradation –two key metrics for benchmark performance of digital …

Rode's Method: Theory and Implementation
06 Jul 2010  Teaching Materials  Contributor(s): Dragica Vasileska
This set of teaching materials provides theoretical description of the Rode's method for the low field mobility calculation that is accompanied with a MATLAB code for the low field mobility calculation for GaAs material at different temperatures and different doping concentrations. Note that the mobility calculated with the Rode method is the transport or the effective mobility whereas Hall measurements provide the Hall mobility. The ratio of the two gives the socalled Hall scattering factor. …

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. …

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 …

Analytical and Numerical Solution of the Double Barrier Problem
28 Jun 2010  Teaching Materials  Contributor(s): Gerhard Klimeck, Parijat Sengupta, Dragica Vasileska
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 – floating gate memories), but in some cases it leads to unwanted power dissipation, such as gate leakage in both MOS and Schottky transistors. Resonant tunneling diodes, due to the tunneling …

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.

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.

Solar Cells Numerical Solution
08 Jun 2010  Teaching Materials  Contributor(s): Dragica Vasileska
This is an MS Thesis of Balaji Padmanabhan, a student of Prof. Vasileska. It describes numerical solution details for the 3D driftdiffusion equations as applied to modeling 1D3D solar cells.

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.

Poisson Equation Solvers
08 Jun 2010  Teaching Materials  Contributor(s): Dragica Vasileska
There are two general schemes for solving linear systems:
Direct Elimination Methods, and
Iterative Methods.
All the direct methods are, in some sense, based on the standard Gauss Elimination technique, which systematically applies row operations to transform the original system of equations into a form that is easier to solve. This section overviews the LU Decomposition method which, although functionally equivalent to the Gauss Elimination method, does provide some additional …

Poisson Equation Solvers  General Considerations
08 Jun 2010  Teaching Materials  Contributor(s): Dragica Vasileska
We describe the need for numerical modeling, the finite difference method, the conversion from continuous set to set of matrix equations, types of solvers for solving sparse matrix equations of the form Ax=b that result, for example, from the finite difference discretization of the Poisson Equation.

Conjugate Gradient Tutorial
08 Jun 2010  Teaching Materials  Contributor(s): Dragica Vasileska
This is an extensive tutorial on the description and implementation of the basic conjugate gradient method and its variants.

Multigrid Tutorial
08 Jun 2010  Teaching Materials  Contributor(s): Dragica Vasileska
This set of slides describe the idea behind the multigrid method and its implementation.

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.

Physical and Mathematical Description of the Operation of Photodetectors
08 Jun 2010  Teaching Materials  Contributor(s): Dragica Vasileska
This set of slides describes physical and mathematical description of the operation of photodetectors including important figures of merit.