Papers by Gerhard Klimeck
… Electronics, 2009. IWCE …, Jan 1, 2009
This work focuses on the determination of the valid device domain for the use of the Top of the b... more 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.
Abstract Semiconductor devices are scaled down to the level which constituent materials are no lo... more Abstract Semiconductor devices are scaled down to the level which constituent materials are no longer considered continuous. To account for atomistic randomness, surface effects and quantum mechanical effects, an atomistic modeling approach needs to be pursued. The Nanoelectronic Modeling Tool (NEMO 3-D) has satisfied the requirement by including empirical sp 3 s* and sp 3 d 5 s* tight binding models and considering strain to successfully simulate various semiconductor material systems.
In the fields of solid-state lighting and high efficiency solar photovoltaics (PVs), a need still... more In the fields of solid-state lighting and high efficiency solar photovoltaics (PVs), a need still exists for a material system that can target the 2.3–2.5 eV energy range. The ZnSe/GaAs system is shown to have great potential. The digital alloy approach can be utilized as a well-ordered design alternative to the disordered alloyed systems. The effective bandgap of the ZnSe/GaAs(001) superlattice has been studied as a function of the constituent monolayers using tight binding.
Si-based devices are being pursued for quantum computing and spintronics due to their scaling pot... more Si-based devices are being pursued for quantum computing and spintronics due to their scaling potential and integrability within the present industrial nanoelectronic infrastructure. Relative energies and degeneracies of valley states are critical for device operation in these novel computing architectures and conventional MOSFET devices at nanometer scale. Bulk Si has six equivalent conduction band minima. In (110) Si quantum wells (QWs), this degeneracy is reduced to 4 fold in effective mass approximation (EMA)[1].
Abstract nanoHUB. org is a major engineering cyber-environment that annually supports over 120,00... more Abstract nanoHUB. org is a major engineering cyber-environment that annually supports over 120,000 users with online simulation and more. Over 8,500 nanoscale engineering and science researchers, educators, and learners run over 340,000 simulations with over 170 simulation tools annually. These tools allows them to transparently and interactively leverage a range of computational resources ranging from small jobs to massive simulations that execute on the Teragrid or the Open Science Grid (OSG).
The calculation of static and dynamic properties of crystal lattices from atomic configurations h... more The calculation of static and dynamic properties of crystal lattices from atomic configurations has a century-long history. 1 Interest in these quantities is currently revived because of the increasing importance of thermal effects in nanodevices. CPU power consumption, combined with increased resource scarcity, poses serious technological challenges for which the quantitative understanding of nanoscale lattice properties is critical.
ABSTRACT Over the last decade, the ongoing improvement of nanofabrication technologies has opened... more ABSTRACT Over the last decade, the ongoing improvement of nanofabrication technologies has opened the way for novel nano-devices and semiconductor structures with sizes of a few tens of nanometers. One realization of such semiconductor devices can be found in the application of quantum dots. Quantum dots are characterized by their ability to confine carriers in all three spatial dimensions on a nanometer scale.
Abstract A homo-junction In 0.53 Ga 0.47 As tunneling diode is investigated using full-band, atom... more Abstract A homo-junction In 0.53 Ga 0.47 As tunneling diode is investigated using full-band, atomistic quantum transport approach based on a tight-binding model (TB) and the non-equilibrium Green's function formalism. Band gap narrowing (BGN) is included in TB by altering its parameters using the Jain-Roulston model [SC Jain and DJ Roulston, Solid-State Electron. 34, 453 (1991)]. BGN is found to be critical in the determination of the current peak and the second turn-on in the forward bias region.
Abstract We present a simulation study of Si nanowire (NW) transistor devices for logic applicati... more Abstract We present a simulation study of Si nanowire (NW) transistor devices for logic applications using an atomistic tight-binding (TB) model for the electronic structure calculation, self consistently coupled to a two-dimensional Poisson solver for the solution of the electrostatics. A semiclassical ballistic model is used for the transport calculation.
Abstract When the physical gate length is reduced to 5 nm, direct channel tunneling dominates the... more Abstract When the physical gate length is reduced to 5 nm, direct channel tunneling dominates the leakage current for both field-effect transistors (FETs) and tunnel FETs. Therefore, a survey of materials in a nanowire geometry is performed to determine their ability to suppress the direct tunnel current through a 5 nm barrier. The materials investigated are InAs, InSb, InP, GaAs, GaN, Si, Ge, and carbon nanotubes.
The simulation of realistically sized devices under the Non-Equilibrium Greens Function (NEGF) fo... more The simulation of realistically sized devices under the Non-Equilibrium Greens Function (NEGF) formalism typically requires prohibitive amounts of memory and computation time. In order to meet the rising computational challenges associated with quantum-scale device simulation we offer a 2-D domain decomposition technique. This technique is applicable to a large class of atomistic and spatial simulation problems.
Abstract Ge exhibits a high bulk hole mobilty making it an attractive channel material for pMOSFE... more Abstract Ge exhibits a high bulk hole mobilty making it an attractive channel material for pMOSFET devices. For improving the device performance and suppressing short channel effects ultra-thin-body (UTB) Ge-on-insulator (GeOI) structures have been researched throughly. Recently<; 110>; oriented Ge-OI pMOSFETs grown on (110) surface were shown to exhibit enhanced hole mobility, which was 3 times compared to (100)/<; 100>; Si and 2.3 times (100)/<; 100>; Ge pMOSFETs.
Abstract Modeling and simulation take an important role in the exploration and design optimizatio... more Abstract Modeling and simulation take an important role in the exploration and design optimization of novel devices. As the downscaling of electronic devices continues, the description of interfaces, randomness, and disorder on an atomistic level gains importance and continuum descriptions lose their validity. Often a full-band description of the electronic structure is needed to model the interaction of different valleys and nonparabolicity effects.
Abstract The development of a DNA field-effect transistor (DNAFET) simulator is described and imp... more Abstract The development of a DNA field-effect transistor (DNAFET) simulator is described and implications on device structure and future experiments are discussed in this paper. In DNAFETs the gate structure is replaced by a layer of immobilized single-stranded DNA molecules which act as surface probe molecules. 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.
Abstract Semiconductor nanowires are possible candidates to replace the metal-oxide-semiconductor... more Abstract Semiconductor nanowires are possible candidates to replace the metal-oxide-semiconductor field-effect transistors (MOSFET) since they can act both as active devices or as device connectors. In this article, the transmission coefficients of Si and GaAs nanowires with arbitrary transport directions and cross sections are simulated in the nearest-neighbor sp 3 d 5 s* semi-empirical tight-binding method.
Abstract One-dimensional (1D) and two-dimensional (2D) metal-oxide-semiconductor field-effect tra... more Abstract One-dimensional (1D) and two-dimensional (2D) metal-oxide-semiconductor field-effect transistors are compared using an approach based on the top-of-the-barrier ballistic transport model. The results for model devices show that 1D and 2D transistors behave quite similarly if the electrostatics is assumed to be perfect. Distinctive features of 1D transport are difficult to observe at room temperature.
Abstract The thermoelectric power-factor (PF) and efficiency (ZT) of GaAs nanowires (NWs) can be ... more Abstract The thermoelectric power-factor (PF) and efficiency (ZT) of GaAs nanowires (NWs) can be improved by (i) choosing a proper wire growth and channel orientation,(ii) by applying uniaxial tensile stress, and (iii) suitable wire cross-section size. In this work we study the impact of these three factors on the PF and the ZT.
Abstract The convergence of electron and hole ground states of a dome-shaped In 0.6 Ga 0.4 As qua... more Abstract The convergence of electron and hole ground states of a dome-shaped In 0.6 Ga 0.4 As quantum dot as a function of the size of the surrounding buffer is explored within an sp 3 d 5 s* tight binding model. It is found that although the quantum dot encompasses only 2× 10 5 atoms, proper convergence of ground state eigenenergies requires that over 10 times as many atoms need to be included in the simulation domain.
Tunneling Field Effect Transistors (TFETs) have been investigated intensively because of its abil... more Tunneling Field Effect Transistors (TFETs) have been investigated intensively because of its ability to reduce the 60meV/dec subthreshold swing (SS) which limits power scaling in conventional MOSFETs. However, tunneling field effect transistors (TFETs) suffer from low Ion, which reduces the speed of TFETs. To increase the Ion and hence the tunneling probability one seeks for efficient ways is to reduce then bandgap [1].
Abstract The atomistic tight binding simulator NEMO 3-D has previously been validated against the... more Abstract The atomistic tight binding simulator NEMO 3-D has previously been validated against the experimental data for quantum dots, wells, and wires in the InGaAlAs and SiGe material systems. Here, we demonstrate our new capability to compute optical matrix elements and transition strengths in tight binding. Systematic multi-million atom electronic structure calculations explore the quantum confined Stark shift and the ground state optical transition rate for an electric field in the lateral [100] direction.
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Papers by Gerhard Klimeck