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Articles 31 - 60 of 133
Full-Text Articles in Nanoscience and Nanotechnology
Feasibility, Accuracy, And Performance Of Contact Block Reduction Method For Multi-Band Simulations Of Ballistic Quantum Transport, Hoon Ryu, Hong-Hyun Park, Mincheol Shin, Dragica Vasileska, Gerhard Klimeck
Feasibility, Accuracy, And Performance Of Contact Block Reduction Method For Multi-Band Simulations Of Ballistic Quantum Transport, Hoon Ryu, Hong-Hyun Park, Mincheol Shin, Dragica Vasileska, Gerhard Klimeck
Gerhard Klimeck
Numerical utilities of the contact block reduction (CBR) method in evaluating the retarded Green’s function are discussed for 3D multi-band open systems that are represented by the atomic tight-binding (TB) and continuum k * p (KP) band model. It is shown that the methodology to approximate solutions of open systems, which has been already reported for the single-band effective mass model, cannot be directly used for atomic TB systems, since the use of a set of zinc blende crystal grids makes the inter-coupling matrix non-invertible. We derive and test an alternative with which the CBR method can be still practical …
Atomistic Full-Band Simulations Of Si Nanowire Transistors: Effects Of Electron-Phonon Scattering, Mathieu Luisier, Gerhard Klimeck
Atomistic Full-Band Simulations Of Si Nanowire Transistors: Effects Of Electron-Phonon Scattering, Mathieu Luisier, Gerhard Klimeck
Gerhard Klimeck
An atomistic full-band quantum transport simulator has been developed to study three-dimensional Si nanowire field-effect transistors (FETs) in the presence of electron-phonon scattering. The Non-equilibrium Green's Function (NEGF) formalism is solved in a nearest-neighbor sp(3)d(5)s* tight-binding basis. The scattering self-energies are derived in the self-consistent Born approximation to inelastically couple the full electron and phonon energy spectra. The band dispersion and the eigenmodes of the confined phonons are calculated using a dynamical matrix that includes the bond and angle deformations of the nanowires. The optimization of the numerical algorithms and the parallelization of the NEGF scheme enable the investigation of …
On The Validity Of The Top Of The Barrier Quantum Transport Model For Ballistic Nanowire Mosfets, Abhijeet Paul, Saumitra Mehrotra, Gerhard Klimeck, Mathieu Luisier
On The Validity Of The Top Of The Barrier Quantum Transport Model For Ballistic Nanowire Mosfets, Abhijeet Paul, Saumitra Mehrotra, Gerhard Klimeck, Mathieu Luisier
Gerhard Klimeck
This work focuses on the determination of the valid device domain for the use of the Top of the barrier (ToB) model to simulate quantum transport in nanowire MOSFETs in the ballistic regime. The presence of a proper Source/Drain barrier in the device is an important criterion for the applicability of the model. Long channel devices can be accurately modeled under low and high drain bias with DIBL adjustment.
Cyber-Enabled Simulations In Nanoscale Science And Engineering Introduction, Alejandro Strachan, Gerhard Klimeck, Mark S. Lundstrom
Cyber-Enabled Simulations In Nanoscale Science And Engineering Introduction, Alejandro Strachan, Gerhard Klimeck, Mark S. Lundstrom
Gerhard Klimeck
Editorial Material
From Nemo1d And Nemo3d To Omen: Moving Towards Atomistic 3-D Quantum Transport In Nano-Scale Semiconductors, Gerhard Klimeck, Mathieu Luisier
From Nemo1d And Nemo3d To Omen: Moving Towards Atomistic 3-D Quantum Transport In Nano-Scale Semiconductors, Gerhard Klimeck, Mathieu Luisier
Gerhard Klimeck
Lessons learned in 15 years of NEMO development starting from quantitative and predictive resonant tunneling diode (RTD) to multi-million atom electronic structure modeling and the path for OMEN are laid out. The recent OMEN capabilities enable realistically large 3D atomistic nano-scale device simulation.
Sub-Threshold Study Of Undoped Trigate Nfinfet, G C. Tettamanzi, G P. Lansbergen, A Paul, Sunhee Lee, P A. Deosarran, N Collaert, Gerhard Klimeck, S Biesemans, S Rogge
Sub-Threshold Study Of Undoped Trigate Nfinfet, G C. Tettamanzi, G P. Lansbergen, A Paul, Sunhee Lee, P A. Deosarran, N Collaert, Gerhard Klimeck, S Biesemans, S Rogge
Gerhard Klimeck
Modern MOSFET devices with undoped channel have a non-trivial current distribution, which is gate voltage dependent In our work we have studied the sub-threshold behavior of undoped triple gate MOSFETs (FinFETs) using a thermionic transport model We have analyzed the conductance data of such devices. and from this, we have been able to determine the evolution of both the active cross-section area of the channel and the barrier height as a function of the gate voltage The result of our experiments shows good agreement with tight binding simulations and with analytical results. This confirms the validity of the use of …
Effects Of Interface Roughness Scattering On Radio Frequency Performance Of Silicon Nanowire Transistors, Sunggeun Kim, Mathieu Luisier, Timothy B. Boykin, Gerhard Klimeck
Effects Of Interface Roughness Scattering On Radio Frequency Performance Of Silicon Nanowire Transistors, Sunggeun Kim, Mathieu Luisier, Timothy B. Boykin, Gerhard Klimeck
Gerhard Klimeck
The effects of an atomistic interface roughness in n-type silicon nanowire transistors (SiNWT) on the radio frequency performance are analyzed. Interface roughness scattering (IRS) is statistically investigated through a three dimensional full–band quantum transport simulation based on the sp3d5s∗ tight–binding model. As the diameter of the SiNWT is scaled down below 3 nm, IRS causes a significant reduction of the cut-off frequency. The fluctuations of the conduction band edge due to the rough surface lead to a reflection of electrons through mode-mismatch. This effect reduces the velocity of electrons and hence the transconductance considerably causing a cut-off frequency reduction.
Advancing Nanoelectronic Device Modeling Through Peta-Scale Computing And Deployment On Nanohub, Benjamin Haley, Sunhee Lee, Mathieu Luisier, Hoon Ryu, Faisal Saied, Steven Clark, Hansang Bae, Gerhard Klimeck
Advancing Nanoelectronic Device Modeling Through Peta-Scale Computing And Deployment On Nanohub, Benjamin Haley, Sunhee Lee, Mathieu Luisier, Hoon Ryu, Faisal Saied, Steven Clark, Hansang Bae, Gerhard Klimeck
Gerhard Klimeck
Recent improvements to existing HPC codes NEMO 3-D and OMEN, combined with access to peta-scale computing resources, have enabled realistic device engineering simulations that were previously infeasible. NEMO 3-D can now simulate 1 billion atom systems, and, using 3D spatial decomposition, scale to 32768 cores. Simulation time for the band structure of an experimental P doped Si quantum computing device fell from 40 minutes to I minute. OMEN can perform fully quantum mechanical transport calculations for real-word UTB FETs on 147,456 cores in roughly 5 minutes. Both of these tools power simulation engines on the nanoHUB, giving the community access …
New Tools For The Direct Characterisation Of Finfets, G. C. Tettamanzi, A. Paul, S. Lee, Gerhard Klimeck, S. Rogge
New Tools For The Direct Characterisation Of Finfets, G. C. Tettamanzi, A. Paul, S. Lee, Gerhard Klimeck, S. Rogge
Gerhard Klimeck
This paper discusses how classical transport theories such as the thermionic emission (Ref. [1]), can be used as a powerful tool for the study and the understanding of the most complex mechanisms of transport in Fin Field Effect Transistors (FinFETs). By means of simple current and differential conductance measurements, taken at different temperatures and different gate voltages (VG's), it is possible to extrapolate the evolution of important parameters such as the spatial region of transport and the height of thermionic barrier at the centre of the channel. Furthermore, if the measurements are used in conjunction with simulated data, it becomes …
Orbital Start Effect And Quantum Confinement Transition Of Donors In Silicon, Rajib Rahman, G. P. Lansbergen, Seung H. Park, J. Verdujin, Gerhard Klimeck, S. Rogge, Lloyd C. L. Hollenberg
Orbital Start Effect And Quantum Confinement Transition Of Donors In Silicon, Rajib Rahman, G. P. Lansbergen, Seung H. Park, J. Verdujin, Gerhard Klimeck, S. Rogge, Lloyd C. L. Hollenberg
Gerhard Klimeck
Adiabatic shuttling of single impurity bound electrons to gate-induced surface states in semiconductors has attracted much attention in recent times, mostly in the context of solid-state quantum computer architecture. A recent transport spectroscopy experiment for the first time was able to probe the Stark shifted spectrum of a single donor in silicon buried close to a gate. Here, we present the full theoretical model involving large-scale quantum mechanical simulations that was used to compute the Stark shifted donor states in order to interpret the experimental data. Use of atomistic tight-binding technique on a domain of over a million atoms helped …
A Comprehensive Atomistic Analysis Of Bandstructure Velocities In Si Nanowires, Neophytos Neophytou, Hans Kosina, Gerhard Klimeck
A Comprehensive Atomistic Analysis Of Bandstructure Velocities In Si Nanowires, Neophytos Neophytou, Hans Kosina, Gerhard Klimeck
Gerhard Klimeck
A 20 band sp3d5s* spin-orbit-coupled, semi-empirical, atomistic tight-binding (TB) model is used with a semi-classical, ballistic transport model, to theoretically examine the bandstructure carrier velocity under non-degenerate conditions in silicon nanowire (NW) transistors. Infinitely long, uniform, cylindrical and rectangular NWs, of cross sectional diameters/sides ranging from 3nm to 12nm are considered. For a comprehensive analysis, n-type and p-type NWs in [100], [110] and [111] transport orientations are examined. The carrier velocities of p-type [110] and [111] NWs increase by a factor of ~2X as the NWs’ diameter scales from D=12nm down to D=3nm. The velocity of n-type [110] NWs also …
Level Spectrum Of Single Gated As Donors, Gabriel P. Lansbergen, Rajib Rahman, J. Caro, N. Collaert, S. Biesemans, Gerhard Klimeck, S. Rogge, L.C. L. Hollenberg
Level Spectrum Of Single Gated As Donors, Gabriel P. Lansbergen, Rajib Rahman, J. Caro, N. Collaert, S. Biesemans, Gerhard Klimeck, S. Rogge, L.C. L. Hollenberg
Gerhard Klimeck
We study the electrical transport through single As donors incorporated in the channel of a FinFET, i.e. a donor in a three-terminal geometry. By means of spectroscopic measurements in conjuction with a NEMO-3D model, we can identify the excited states and associate them with either the donors Coulomb potential, a triangular well at the interface or a hybridized combination of the two. The correspondence between the transport measurements, the theoretical model and the local environment provides an atomic understanding of actual gated donors in a nanostructure.
Effects Of Interface Disorder On Valley Splitting In Sige/Si/Sige Quantum Wells, Zhengping Jiang, Neerav Kharche, Timothy Boykin, Gerhard Klimeck
Effects Of Interface Disorder On Valley Splitting In Sige/Si/Sige Quantum Wells, Zhengping Jiang, Neerav Kharche, Timothy Boykin, Gerhard Klimeck
Gerhard Klimeck
A sharp potential barrier at the Si/SiGe interface introduces valley splitting (VS), which lifts the 2-fold valley degeneracy in strained SiGe/Si/SiGe quantum wells (QWs). This work examines in detail the effects of Si/SiGe interface disorder on the VS in an atomistic tight binding approach based on statistical sampling. VS is analyzed as a function of electric field, QW thickness, and simulation domain size. Strong electric fields push the electron wavefunctions into the SiGe buffer and introduce significant VS fluctuations from device to device. A Gedankenexperiment with ordered alloys sheds light on the importance of different bonding configurations on VS. We …
Structures And Energetics Of Silicon Nanotubes From Molecular Dynamics And Density Functional Theory, Amritanshu Palaria, Gerhard Klimeck, Alejandro Strachan
Structures And Energetics Of Silicon Nanotubes From Molecular Dynamics And Density Functional Theory, Amritanshu Palaria, Gerhard Klimeck, Alejandro Strachan
Gerhard Klimeck
We use molecular dynamics with a first-principles-based force field and density functional theory to predict the atomic structure, energetics, and elastic properties of Si nanotubes. We find various low-energy and low-symmetry hollow structures with external diameters of about 1 nm. These are the most stable structures in this small-diameter regime reported so far and exhibit properties very different from the bulk. While the cohesive energies of the four most stable nanotubes reported here are similar (from 0.638 to 0.697 eV above bulk Si), they have disparate Young's moduli (from 72 to 123 GPa).
Non-Primitive Rectangular Cells For Tight-Binding Electronic Structure Calculations, Timothy Boykin, Neerav Kharche, Gerhard Klimeck
Non-Primitive Rectangular Cells For Tight-Binding Electronic Structure Calculations, Timothy Boykin, Neerav Kharche, Gerhard Klimeck
Gerhard Klimeck
Rectangular non-primitive unit cells are computationally convenient for use in nanodevice electronic structure and transport calculations. When these cells are used for Calculations of structures with periodicity, the resulting bands are zone-folded and must be unfolded in order to identify important gaps and masses. Before the zone-unfolding method can be applied, one must first determine the allowed wavevectors for the specific non-primitive cell. Because most computationally convenient non-primitive cells do not have axes parallel to the primitive cell direct lattice vectors, finding the allowed wavevectors is generally a non-trivial task. (Solid state texts generally treat only the simplest case in …
Distributed Negf Algorithms For The Simulation Of Nanoelectronic Devices With Scattering, Stephen Cauley, Mathieu Luisier, Venkataramanan Balakrishnan, Gerhard Klimeck, Cheng-Kok Koh
Distributed Negf Algorithms For The Simulation Of Nanoelectronic Devices With Scattering, Stephen Cauley, Mathieu Luisier, Venkataramanan Balakrishnan, Gerhard Klimeck, Cheng-Kok Koh
Gerhard Klimeck
Through the Non-Equilibrium Green’s Function (NEGF) formalism, quantum- scale device simulation can be performed with the inclusion of electron-phonon scattering. However, the simulation of realistically sized devices under the NEGF formalism typically requires prohibitive amounts of memory and computation time. Two of the most demanding computational problems for NEGF simulation involve mathematical operations with structured matrices called semiseparable matrices. In this work, we present parallel approaches for these computational problems which allow for efficient distribution of both memory and computation based upon the underlying device structure. This is critical when simulating realistically sized devices due to the aforementioned computational burdens. …
Lifetime Enhanced Transport In Silicon Due To Spin And Valley Blockade, Gabriel Lansbergen, Rajib Rahman, J. Verdujin, Giuseppe Tettamanzi, Nadine Collaert, Serge Biesemans, Gerhard Klimeck, Lloyd Hollenberg, Sven Rogge
Lifetime Enhanced Transport In Silicon Due To Spin And Valley Blockade, Gabriel Lansbergen, Rajib Rahman, J. Verdujin, Giuseppe Tettamanzi, Nadine Collaert, Serge Biesemans, Gerhard Klimeck, Lloyd Hollenberg, Sven Rogge
Gerhard Klimeck
We report the observation of Lifetime Enhanced Transport (LET) based on perpendicular valleys in silicon by transport spectroscopy measurements of a two-electron system in a silicon transistor. The LET is manifested as a peculiar current step in the stability diagram due to a forbidden transition between an excited state and any of the lower energy states due perpendicular valley (and spin) configurations, offering an additional current path. By employing a detailed temperature dependence study in combination with a rate equation model, we estimate the lifetime of this particular state to exceed 48 ns. The two-electron spin-valley configurations of all relevant …
Developing A Crystal Viewer Tool For Nanohub, Osiris V. Ntarugera, Gerhard Klimeck
Developing A Crystal Viewer Tool For Nanohub, Osiris V. Ntarugera, Gerhard Klimeck
Gerhard Klimeck
Most materials found in nature have their atoms arranged in a regular and repeated pattern known as crystalline structure; this is particularly true for metals. It is very important to understand the crystal structure of materials in order to predict their properties such as the electric conductivity, heat transfer, and more. Particularly, students and scholars in the field of material science need a way to visualize the different crystal structures. Atomic structures of elements are not visible to the naked eye. In that context, a computer based tool can be used to simulate and to visualize the crystal structures of …
Abacus And Aqme: Semiconductor Device And Quantum Mechanics Education On Nanohub.Org, Gerhard Klimeck, Dragica Vasileska
Abacus And Aqme: Semiconductor Device And Quantum Mechanics Education On Nanohub.Org, Gerhard Klimeck, Dragica Vasileska
Gerhard Klimeck
The ABACUS and AQME on-line tools and their associated wiki pages form one-stop shops for educators and students of existing university courses. They are geared towards courses like "introduction to Semiconductor Devices" and "Quantum Mechanics for Engineers". The service is free to anyone and no software installation is required on the user's computer. All simulations, including advanced visualization are performed at a remote computer. The tools have been deployed on nanoHUB.org in August 2008 and haven already been used by over 700 users. This paper describes nanoHUB educational tool user requirements and the motivation for and some details about these …
Orbital Stark Effect And Quantum Confinement Transition Of Donors In Silicon, Rajib Rahman, G P. Lansbergen, Seung H. Park, J Verduijn, Gerhard Klimeck, S Rogge, Lloyd Cl Hollenberg
Orbital Stark Effect And Quantum Confinement Transition Of Donors In Silicon, Rajib Rahman, G P. Lansbergen, Seung H. Park, J Verduijn, Gerhard Klimeck, S Rogge, Lloyd Cl Hollenberg
Gerhard Klimeck
Adiabatic shuttling of single impurity bound electrons to gate-induced surface states in semiconductors has attracted much attention in recent times, mostly in the context of solid-state quantum computer architecture. A recent transport spectroscopy experiment for the first time was able to probe the Stark shifted spectrum of a single donor in silicon buried close to a gate. Here, we present the full theoretical model involving large-scale quantum mechanical simulations that was used to compute the Stark shifted donor states in order to interpret the experimental data. Use of atomistic tight-binding technique on a domain of over a million atoms helped …
Valley Degeneracies In (111) Silicon Quantum Wells, Neerav Kharche, Seongmin Kim, Timothy B. Boykin, Gerhard Klimeck
Valley Degeneracies In (111) Silicon Quantum Wells, Neerav Kharche, Seongmin Kim, Timothy B. Boykin, Gerhard Klimeck
Gerhard Klimeck
(111) silicon quantum wells have been studied extensively, yet no convincing explanation exists for the experimentally observed breaking of sixfold valley degeneracy into two- and fourfold degeneracies. Here, systematic sp(3)d(5)s(*) tight-binding and effective mass calculations are presented to show that a typical miscut modulates the energy levels, which leads to breaking of sixfold valley degeneracy into two lower and four raised valleys. An effective mass based valley-projection model is used to determine the directions of valley minima in tight-binding calculations of large supercells. Tight-binding calculations are in better agreement with experiments compared to effective mass calculations.
Investigation Of Device Parameters For Field-Effect Dna-Sensors By Three-Dimensional Simulation, Eddie Howell, Clemens Heitzinger, Gerhard Klimeck
Investigation Of Device Parameters For Field-Effect Dna-Sensors By Three-Dimensional Simulation, Eddie Howell, Clemens Heitzinger, Gerhard Klimeck
Gerhard Klimeck
The development of a DNA field-effect transistor (DNAFET) simulator is described and implications on device structure and future experiments are discussed. In DNAFETs the gate structure is replaced by a layer of immobilized single-stranded DNA molecules which act as surface probe molecules [1, 2]. When complementary DNA strands bind to the receptors, the charge distribution near the surface of the device changes, modulating current transport through the device and enabling detection (cf. Fig. 1 and 5). Arrays of DNAFETs can be used for detecting singlenucleotide polymorphisms and for DNA sequencing. The advantage of DNAFETs over optical methods of detection is …
Ohm's Law Survives To The Atomic Scale, B. Weber, S. Mahapatra, H. Ryu, S. Lee, A. Fuhrer, T. C.G. Reusch, D. L. Thompson, W. C.T. Lee, Gerhard Klimeck, L. C. L. Hollenberg, M. Y. Simmons
Ohm's Law Survives To The Atomic Scale, B. Weber, S. Mahapatra, H. Ryu, S. Lee, A. Fuhrer, T. C.G. Reusch, D. L. Thompson, W. C.T. Lee, Gerhard Klimeck, L. C. L. Hollenberg, M. Y. Simmons
Gerhard Klimeck
As silicon electronics approaches the atomic scale, interconnects and circuitry become comparable in size to the active device components. Maintaining low electrical resistivity at this scale is challenging because of the presence of confining surfaces and interfaces. We report on the fabrication of wires in silicon—only one atom tall and four atoms wide—with exceptionally low resistivity (~0.3 milliohm-centimeters) and the current-carrying capabilities of copper. By embedding phosphorus atoms within a silicon crystal with an average spacing of less than 1 nanometer, we achieved a diameter-independent resistivity, which demonstrates ohmic scaling to the atomic limit. Atomistic tight-binding calculations confirm the metallicity …
Electronic Structure Of Realistically Extended Atomistically Resolved Disordered Si:P Δ-Doped Layers, Sunhee Lee, Hoon Ryu, Llyd C. L. Hollenberg, Michelle Y. Simmons, Gerhard Klimeck
Electronic Structure Of Realistically Extended Atomistically Resolved Disordered Si:P Δ-Doped Layers, Sunhee Lee, Hoon Ryu, Llyd C. L. Hollenberg, Michelle Y. Simmons, Gerhard Klimeck
Gerhard Klimeck
The emergence of scanning tunneling microscope (STM) lithography and low temperature molecular beam epitaxy (MBE) opens the possibility of creating scalable donor based quantum computing architectures. In particular, atomically precise Si:P monolayer structures (δ-doped layers) serve as crucial contact regions and in-plane gates in single impurity devices. In this paper we study highly confined δ-doped layers to explain the disorder in the P dopant placements in realistically extended systems. The band structure is computed using the tight-binding formalism and charge-potential self-consistency. The exchange-correlation corrected impurity potential pulls down subbands below the silicon valley minima to create impurity bands. Our methodology …
Silicon Quantum Electronics, Floris A. Zwanenburg, Andrew S. Dzurak, Andrea Morello, Michelle Y. Simmons, Lloyd C. L. Hollenberg, Gerhard Klimeck, Sven Rogge, Susan N. Coppersmith, Mark A. Eriksson
Silicon Quantum Electronics, Floris A. Zwanenburg, Andrew S. Dzurak, Andrea Morello, Michelle Y. Simmons, Lloyd C. L. Hollenberg, Gerhard Klimeck, Sven Rogge, Susan N. Coppersmith, Mark A. Eriksson
Gerhard Klimeck
This review describes recent groundbreaking results in Si, Si/SiGe, and dopant-based quantum dots, and it highlights the remarkable advances in Si-based quantum physics that have occurred in the past few years. This progress has been possible thanks to materials development of Si quantum devices, and the physical understanding of quantum effects in silicon. Recent critical steps include the isolation of single electrons, the observation of spin blockade, and single-shot readout of individual electron spins in both dopants and gated quantum dots in Si. Each of these results has come with physics that was not anticipated from previous work in other …
Laser Bandwidth-Induced Fluctuations In The Intensity Transmitted By A Fabry-Perot Interferometer, Gerhard Klimeck, Daniel Elliott, M. Hamilton
Laser Bandwidth-Induced Fluctuations In The Intensity Transmitted By A Fabry-Perot Interferometer, Gerhard Klimeck, Daniel Elliott, M. Hamilton
Gerhard Klimeck
We have measured the power spectrum of the intensity Auctuations of light transmitted by a Fabry- Perot interferometer when the input field is the real Gaussian field. The real Gaussian field is a field characterized by real, random (Gaussian) amplitude Auctuations. The bandwidth of the real Gaussian field was varied, taking on values less than that of the interferometer, as well as greater. Comparisons of the measured spectra with calculated spectra are quite satisfactory. Of special interest is a feature in the spectra centered at the laser-interferometer detuning frequency.
Spin-Orbit Splittings In Si/Sige Quantum Wells: From Ideal Si Membranes To Realistic Hterostructures, M. Prada, G. Klimeck, R. Joynt
Spin-Orbit Splittings In Si/Sige Quantum Wells: From Ideal Si Membranes To Realistic Hterostructures, M. Prada, G. Klimeck, R. Joynt
Gerhard Klimeck
We present a calculation of the wavevector-dependent subband level splitting from spin-orbit coupling in Si/SiGe quantum wells. We first use the effective-mass approach, where the splittings are parameterized by separating contributions from the Rashba and Dresselhaus terms. We then determine the inversion asymmetry parameters by fitting tight-binding numerical results obtained using the quantitative nanoelectronic modeling tool, NEMO-3D. We describe the relevant coefficients as a function of applied electric field and well width in our numerical simulations. Symmetry arguments can also predict the behavior, and an extensive analysis is also presented in this work. Using vast computational resources, we treat alloy …
Experimental And Atomistic Theoretical Study Of Degree Of Polarization From Multilayer Inas/Gaas Quantum Dot Stacks, Muhammad Usman, Tomoya Inoue, Yukihiro Harda, Gerhard Klimeck, Takashi Kita
Experimental And Atomistic Theoretical Study Of Degree Of Polarization From Multilayer Inas/Gaas Quantum Dot Stacks, Muhammad Usman, Tomoya Inoue, Yukihiro Harda, Gerhard Klimeck, Takashi Kita
Gerhard Klimeck
Recent experimental measurements, without any theoretical guidance, showed that isotropic po- larization response can be achieved by increasing the number of QD layers in a QD stack. Here we analyse the polarization response of multi-layer quantum dot stacks containing up to nine quan- tum dot layers by linearly polarized PL measurements and by carrying out a systematic set of multi-million atom simulations. The atomistic modeling and simulations allow us to include cor- rect symmetry properties in the calculations of the optical spectra: a factor critical to explain the experimental evidence. The values of the degree of polarization (DOP) calculated from …
Shape And Orientation Effects On The Ballistic Phonon Thermal Properties Of Ultra-Scaled Si Nanowires, Abhijeet Paul, Mathieu Luisier, Gerhard Klimeck
Shape And Orientation Effects On The Ballistic Phonon Thermal Properties Of Ultra-Scaled Si Nanowires, Abhijeet Paul, Mathieu Luisier, Gerhard Klimeck
Gerhard Klimeck
The effect of geometrical confinement, atomic position and orientation of Silicon nanowires (SiNWs) on their thermal properties are investigated using the phonon dispersion obtained using a Modified Valence Force Field (MVFF) model. The spe- cific heat (Cv) and the ballistic thermal conductance (κbal) shows anisotropic variation l with changing cross-section shape and size of the SiNWs. The Cv increases with de- creasing cross-section size for all the wires. The triangular wires show the largest Cv due to their highest surface-to-volume ratio. The square wires with [110] orientation show the maximum κbal since they have the highest number of conducting phonon …
Subband Engineering For P-Type Silicon Ultra-Thin Layers For Increased Carrier Velocities: An Atomistic Analysis, Neophytos Neophytou, Gerhard Klimeck
Subband Engineering For P-Type Silicon Ultra-Thin Layers For Increased Carrier Velocities: An Atomistic Analysis, Neophytos Neophytou, Gerhard Klimeck
Gerhard Klimeck
Ultra-thin-body (UTB) channel materials of a few nanometers in thickness are currently considered as candidates for future electronic, thermoelectric, and optoelectronic applications. Among the features that they possess, which make them attractive for such applications, their confinement length scale, transport direction, and confining surface orientation serve as degrees of freedom for engineering their electronic properties. This work presents a comprehensive study of hole velocities in p-type UTB films of widths from 15 nm down to 3 nm. Various transport and surface orientations are considered. The atomistic sp3d5s*-spin-orbit-coupled tight-binding model is used for the electronic structure, and a semiclassical ballistic model …