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Nanoelectronic Modeling Lecture 24: NEMO1D - Incoherent Scattering

09 Mar 2010 | Online Presentations | Contributor(s): Gerhard Klimeck

Incoherent processes due to phonons, interface roughness and disorder had been suspected to be the primary source of the valley current of resonant tunneling diodes (RTDs) at the beginning of the NEMO1D project in 1994. The modeling tool NEMO was created at Texas Instruments to fundamentally...

Nanoelectronic Modeling Lecture 23: NEMO1D - Importance of New Boundary Conditions

One of the key insights gained during the NEMO1D project was the development of new boundary conditions that enabled the modeling of realistically extended Resonant Tunneling Diodes (RTDs). The new boundary conditions are based on the partitioning of the device into emitter and collector...

Nanoelectronic Modeling Lecture 22: NEMO1D - Motivation, History and Key Insights

07 Feb 2010 | Online Presentations | Contributor(s): Gerhard Klimeck

The primary objective of the NEMO-1D tool was the quantitative modeling of high performance Resonant Tunneling Diodes (RTDs). The software tool was intended for Engineers (concepts, fast turn-around, interactive) and Scientists (detailed device anaysis). Therefore various degrees of...

Nanoelectronic Modeling Lecture 21: Recursive Green Function Algorithm

The Recursive Green Function (RGF) algorithms is the primary workhorse for the numerical solution of NEGF equations in quasi-1D systems. It is particularly efficient in cases where the device is partitioned into reservoirs which may be characterized by a non-Hermitian Hamiltonian and a central...

Nanoelectronic Modeling nanoHUB Demo 1: nanoHUB Tool Usage with RTD Simulation with NEGF

Demonstration of running tools on the nanoHUB. Demonstrated is the RTD Simulation with NEGF Tool using a simple level-drop potential model and a more realistic device using a Thomas-Fermi potential model.

Nanoelectronic Modeling nanoHUB Demo 2: RTD simulation with NEGF

Demonstration of resonant tunneling diode (RTD) simulation using the RTD Simulation with NEGF Tool with a Hartree potential model showing potential profile, charge densities, current-voltage characteristics, and resonance energies. Also demonstrated is a RTD simulation using a Thomas-Fermi...

ECE 694A: Professional Development Seminar Series

17 Feb 2010 | Series | Contributor(s): Gerhard Klimeck

The ECE Graduate Seminar, ECE 694, is designed to provide opportunities for professional development of graduate sudents, raise their awareness of various other issues that they may face in their professional careers, and provide them opportunities to survey research seminars of their interest.

Nanoelectronic Modeling: Exercises 1-3 - Barrier Structures, RTDs, and Quantum Dots

27 Jan 2010 | Online Presentations | Contributor(s): Gerhard Klimeck

Exercises:Barrier StructuresUses: Piece-Wise Constant Potential Barrier ToolResonant Tunneling DiodesUses: Resonant Tunneling Diode Simulation with NEGF • Hartree calculation • Thomas Fermi potentialQuantum DotsUses: Quantum Dot Lab • pyramidal dot

Nanoelectronic Modeling Lecture 20: NEGF in a Quasi-1D Formulation

27 Jan 2010 | Online Presentations | Contributor(s): Gerhard Klimeck, Samarth Agarwal, Zhengping Jiang

This lecture will introduce a spatial discretization scheme of the Schrödinger equation which represents a 1D heterostructure like a resonant tunneling diode with spatially varying band edges and effective masses.

Nanoelectronic Modeling Lecture 19: Introduction to RTDs - Asymmetric Structures

This lecture explores this effect in more detail by targeting an RTD that has a deliberate asymmetric structure. The collector barrier is chosen thicker than the emitter barrier. With this set-up we expect that the tunneling rate into the RTD from the emitter is faster than the tunneling rate...

Nanoelectronic Modeling Lecture 18: Introduction to RTDs - Quantum Charge Self-Consistency (Hartree)

In this semi-classical charge and potential model the quantum mechanical simulation is performed once and the quantum mechanical charge is in general not identical to the semi-classical charge.

Nanoelectronic Modeling Lecture 17: Introduction to RTDs - Relaxation Scattering in the Emitter

Realistic RTDs will have nonlinear electrostatic potential in their emitter. Typically a triangular well is formed in the emitter due to the applied bias and the emitter thus contains discrete quasi bound states.

Nanoelectronic Modeling Lecture 16: Introduction to RTDs - Realistic Doping Profiles

Realistic RTDs need extremely high doping to provide enough carriers for high current densities. However, Impurity scattering can destroy the RTD performance. The dopants are therefore typically spaced 20-100nm away from the central double barrier structure.

Nanoelectronic Modeling Lecture 14: Open 1D Systems - Formation of Bandstructure

27 Jan 2010 | Online Presentations | Contributor(s): Gerhard Klimeck, Dragica Vasileska

The infinite periodic structure Kroenig Penney model is often used to introduce students to the concept of bandstructure formation. It is analytically solvable for linear potentials and shows critical elements of bandstructure formation such as core bands and different effective masses in...

Nanoelectronic Modeling Lecture 12: Open 1D Systems - Transmission through Double Barrier Structures - Resonant Tunneling

This presentation shows that double barrier structures can show unity transmission for energies BELOW the barrier height, resulting in resonant tunneling. The resonance can be associated with a quasi bound state, and the bound state can be related to a simple particle in a box calculation.

Nanoelectronic Modeling Lecture 11: Open 1D Systems - The Transfer Matrix Method

31 Dec 2009 | Online Presentations | Contributor(s): Gerhard Klimeck, Dragica Vasileska, Samarth Agarwal, Parijat Sengupta

The transfer matrix approach is analytically exact, and “arbitrary” heterostructures can apparently be handled through the discretization of potential changes. The approach appears to be quite appealing. However, the approach is inherently unstable for realistically extended devices which...

Nanoelectronic Modeling Lecture 10: Open 1D Systems - Transmission through & over 1 Barrier

31 Dec 2009 | Online Presentations | Contributor(s): Gerhard Klimeck, Dragica Vasileska, Samarth Agarwal

Tunneling and interference are critical in the understanding of quantum mechanical systems. The 1D time independent Schrödinger equation can be easily solved analytically in a scattering matrix approach for a system of a single potential barrier. The solution is obtained by matching wavefunction...

Nanoelectronic Modeling Lecture 09: Open 1D Systems - Reflection at and Transmission over 1 Step

25 Jan 2010 | Online Presentations | Contributor(s): Gerhard Klimeck, Dragica Vasileska, Samarth Agarwal

One of the most elemental quantum mechanical transport problems is the solution of the time independent Schrödinger equation in a one-dimensional system where one of the two half spaces has a higher potential energy than the other. The analytical solution is readily obtained using a scattering...

Nanoelectronic Modeling Lecture 08: Introduction to Bandstructure Engineering II

25 Jan 2010 | Online Presentations | Contributor(s): Gerhard Klimeck

This presentation provides a brief overview of the concepts of bandstructure engineering and its potential applications to light detectors, light emitters, and electron transport devices. Critical questions of the origin of bandstructure and its dependence on local atom arrangements are raised...

Nanoelectronic Modeling Lecture 07: Introduction to Bandstructure Engineering I

This presentation serves as a reminder about basic quantum mechanical principles without any real math. The presentation reviews critical properties of classical systems that can be described as particles, propagating waves, standing waves, and chromatography.

Nanoelectronic Modeling Lecture 06: nanoHUB.org - Rappture Toolkit

25 Jan 2010 | Online Presentations | Contributor(s): Gerhard Klimeck, Michael McLennan

The rapid deployment of over 150 simulation tools in just over 4 years has been enabled by 2 critical software developments: 1) Maxwell’s Daemon: a middleware that can deploy at a production level UNIX based codes in web browsers, and 2) Rappture: a software system that enables the rapid...

Nanoelectronic Modeling Lecture 05: nanoHUB.org - Impact on Research

Impact on research is often measured by the number of publications in the scientific literature. The nanoHUB support team has identified 430 citations to nanoHUB.org and/or nanoHUB tools and seminars in the time frame leading up to May 2008 the 430 citations in the scientific literature. 52% of...

Nanoelectronic Modeling Lecture 04: nanoHUB.org - Impact on Education

This presentation will provide a few highlights of how nanoHUB.org is being used in education and what kind of impact it has had so far. Tools and seminars are indeed being used as instructional materials. nanoHUB has been used in over 290 classes in the past few years in over 90 institutions...

Nanoelectronic Modeling Lecture 03: nanoHUB.org - Online Simulation and More

This presentation provides a brief overview of the nanoHUB capabilites, compares it to static web page delivery, highlights its technology basis, and provides a vision for future cyberinfrastructures in a system of federated HUBs powered by the HUBzero.org infrastructure.

Nanoelectronic Modeling Lecture 02: (NEMO) Motivation and Background

25 Jan 2010 | Online Presentations | Contributor(s): Gerhard Klimeck, Dragica Vasileska

Fundamental device modeling on the nanometer scale must include effect of open systems, high bias, and an atomistic basis. The non-equilibrium Green Function Formalism (NEGF) can include all these components in a fundamentally sound approach and has been the basis for a few novel device...