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Mark Lundstrom - One of the best experts on this subject based on the ideXlab platform.
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Simulations of nanowire transistors: atomistic vs. Effective Mass models
Journal of Computational Electronics, 2008Co-Authors: Neophytos Neophytou, Mark Lundstrom, Abhijeet Paul, Gerhard KlimeckAbstract:The ballistic performance of electron transport in nanowire transistors is examined using a 10 orbital sp3d5s* atomistic tight-binding model for the description of the electronic structure, and the top-of-the-barrier semiclassical ballistic model for calculation of the transport properties of the transistors. The dispersion is self consistently computed with a 2D Poisson solution for the electrostatic potential in the cross section of the wire. The Effective Mass of the nanowire changes significantly from the bulk value under strong quantization, and effects such as valley splitting strongly lift the degeneracies of the valleys. These effects are pronounced even further under filling of the lattice with charge. The Effective Mass Approximation is in good agreement with the tight binding model in terms of current–voltage characteristics only in certain cases. In general, for small diameter wires, the Effective Mass Approximation fails.
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on the validity of the parabolic Effective Mass Approximation for the i v calculation of silicon nanowire transistors
IEEE Transactions on Electron Devices, 2005Co-Authors: Jing Wang, Anisur Rahman, Avik W Ghosh, Gerhard Klimeck, Mark LundstromAbstract:This paper examines the validity of the widely used parabolic Effective-Mass Approximation for computing the current-voltage (I-V) characteristics of silicon nanowire transistors (SNWTs). The energy dispersion relations for unrelaxed Si nanowires are first computed by using an sp/sup 3/d/sup 5/s/sup */ tight-binding (TB) model. A seminumerical ballistic field-effect transistor model is then adopted to evaluate the I-V characteristics of the (n-type) SNWTs based on both a TB dispersion relation and parabolic energy bands. In comparison with the TB approach, the parabolic Effective-Mass model with bulk Effective-Masses significantly overestimates SNWT threshold voltages when the wire width is <3 nm, and ON-currents when the wire width is <5 nm. By introducing two analytical equations with two tuning parameters, however, the Effective-Mass Approximation can well reproduce the TB I-V results even at a /spl sim/1.36-nm wire width.
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On the validity of the parabolic Effective-Mass Approximation for the I-V calculation of silicon nanowire transistors
IEEE Transactions on Electron Devices, 2005Co-Authors: Jing Wang, Anisur Rahman, Gerhard Klimeck, A. Ghosh, Mark LundstromAbstract:This paper examines the validity of the widely used parabolic Effective-Mass Approximation for computing the current-voltage (I-V) characteristics of silicon nanowire transistors (SNWTs). The energy dispersion relations for unrelaxed Si nanowires are first computed by using an sp/sup 3/d/sup 5/s/sup */ tight-binding (TB) model. A seminumerical ballistic field-effect transistor model is then adopted to evaluate the I-V characteristics of the (n-type) SNWTs based on both a TB dispersion relation and parabolic energy bands. In comparison with the TB approach, the parabolic Effective-Mass model with bulk Effective-Masses significantly overestimates SNWT threshold voltages when the wire width is
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on the validity of the parabolic Effective Mass Approximation for the current voltage calculation of silicon nanowire transistors
arXiv: Mesoscale and Nanoscale Physics, 2004Co-Authors: Jing Wang, Anisur Rahman, Avik W Ghosh, Gerhard Klimeck, Mark LundstromAbstract:This paper examines the validity of the widely-used parabolic Effective-Mass Approximation for computing the current-voltage (I-V) characteristics of silicon nanowire transistors (SNWTs). The energy dispersion relations for unrelaxed Si nanowires are first computed by using an sp3d5s* tight-binding model. A semi-numerical ballistic FET model is then adopted to evaluate the I-V characteristics of the (n-type) SNWTs based on both a tight-binding dispersion relation and parabolic energy bands. In comparison with the tight-binding approach, the parabolic Effective-Mass model with bulk Effective-Masses significantly overestimates SNWT threshold voltages when the wire width is <3nm, and ON-currents when the wire width is <5nm. By introducing two analytical equations with two tuning parameters, however, the Effective-Mass Approximation can well reproduce the tight-binding I-V results even at a \~1.36nm wire with.
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a three dimensional quantum simulation of silicon nanowire transistors with the Effective Mass Approximation
Journal of Applied Physics, 2004Co-Authors: Jing Wang, Eric Polizzi, Mark LundstromAbstract:The silicon nanowire transistor (SNWT) is a promising device structure for future integrated circuits, and simulations will be important for understanding its device physics and assessing its ultimate performance limits. In this work, we present a three-dimensional (3D) quantum mechanical simulation approach to treat various SNWTs within the Effective-Mass Approximation. We begin by assuming ballistic transport, which gives the upper performance limit of the devices. The use of a mode space approach (either coupled or uncoupled) produces high computational efficiency that makes our 3D quantum simulator practical for extensive device simulation and design. Scattering in SNWTs is then treated by a simple model that uses so-called Buttiker probes, which was previously used in metal-oxide-semiconductor field effect transistor simulations. Using this simple approach, the effects of scattering on both internal device characteristics and terminal currents can be examined, which enables our simulator to be used f...
Jing Wang - One of the best experts on this subject based on the ideXlab platform.
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on the validity of the parabolic Effective Mass Approximation for the i v calculation of silicon nanowire transistors
IEEE Transactions on Electron Devices, 2005Co-Authors: Jing Wang, Anisur Rahman, Avik W Ghosh, Gerhard Klimeck, Mark LundstromAbstract:This paper examines the validity of the widely used parabolic Effective-Mass Approximation for computing the current-voltage (I-V) characteristics of silicon nanowire transistors (SNWTs). The energy dispersion relations for unrelaxed Si nanowires are first computed by using an sp/sup 3/d/sup 5/s/sup */ tight-binding (TB) model. A seminumerical ballistic field-effect transistor model is then adopted to evaluate the I-V characteristics of the (n-type) SNWTs based on both a TB dispersion relation and parabolic energy bands. In comparison with the TB approach, the parabolic Effective-Mass model with bulk Effective-Masses significantly overestimates SNWT threshold voltages when the wire width is <3 nm, and ON-currents when the wire width is <5 nm. By introducing two analytical equations with two tuning parameters, however, the Effective-Mass Approximation can well reproduce the TB I-V results even at a /spl sim/1.36-nm wire width.
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On the validity of the parabolic Effective-Mass Approximation for the I-V calculation of silicon nanowire transistors
IEEE Transactions on Electron Devices, 2005Co-Authors: Jing Wang, Anisur Rahman, Gerhard Klimeck, A. Ghosh, Mark LundstromAbstract:This paper examines the validity of the widely used parabolic Effective-Mass Approximation for computing the current-voltage (I-V) characteristics of silicon nanowire transistors (SNWTs). The energy dispersion relations for unrelaxed Si nanowires are first computed by using an sp/sup 3/d/sup 5/s/sup */ tight-binding (TB) model. A seminumerical ballistic field-effect transistor model is then adopted to evaluate the I-V characteristics of the (n-type) SNWTs based on both a TB dispersion relation and parabolic energy bands. In comparison with the TB approach, the parabolic Effective-Mass model with bulk Effective-Masses significantly overestimates SNWT threshold voltages when the wire width is
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on the validity of the parabolic Effective Mass Approximation for the current voltage calculation of silicon nanowire transistors
arXiv: Mesoscale and Nanoscale Physics, 2004Co-Authors: Jing Wang, Anisur Rahman, Avik W Ghosh, Gerhard Klimeck, Mark LundstromAbstract:This paper examines the validity of the widely-used parabolic Effective-Mass Approximation for computing the current-voltage (I-V) characteristics of silicon nanowire transistors (SNWTs). The energy dispersion relations for unrelaxed Si nanowires are first computed by using an sp3d5s* tight-binding model. A semi-numerical ballistic FET model is then adopted to evaluate the I-V characteristics of the (n-type) SNWTs based on both a tight-binding dispersion relation and parabolic energy bands. In comparison with the tight-binding approach, the parabolic Effective-Mass model with bulk Effective-Masses significantly overestimates SNWT threshold voltages when the wire width is <3nm, and ON-currents when the wire width is <5nm. By introducing two analytical equations with two tuning parameters, however, the Effective-Mass Approximation can well reproduce the tight-binding I-V results even at a \~1.36nm wire with.
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a three dimensional quantum simulation of silicon nanowire transistors with the Effective Mass Approximation
Journal of Applied Physics, 2004Co-Authors: Jing Wang, Eric Polizzi, Mark LundstromAbstract:The silicon nanowire transistor (SNWT) is a promising device structure for future integrated circuits, and simulations will be important for understanding its device physics and assessing its ultimate performance limits. In this work, we present a three-dimensional (3D) quantum mechanical simulation approach to treat various SNWTs within the Effective-Mass Approximation. We begin by assuming ballistic transport, which gives the upper performance limit of the devices. The use of a mode space approach (either coupled or uncoupled) produces high computational efficiency that makes our 3D quantum simulator practical for extensive device simulation and design. Scattering in SNWTs is then treated by a simple model that uses so-called Buttiker probes, which was previously used in metal-oxide-semiconductor field effect transistor simulations. Using this simple approach, the effects of scattering on both internal device characteristics and terminal currents can be examined, which enables our simulator to be used f...
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a three dimensional quantum simulation of silicon nanowire transistors with the Effective Mass Approximation
arXiv: Other Condensed Matter, 2004Co-Authors: Jing Wang, Eric Polizzi, Mark LundstromAbstract:The silicon nanowire transistor (SNWT) is a promising device structure for future integrated circuits, and simulations will be important for understanding its device physics and assessing its ultimate performance limits. In this work, we present a three-dimensional quantum mechanical simulation approach to treat various SNWTs within the Effective-Mass Approximation. We begin by assuming ballistic transport, which gives the upper performance limit of the devices. The use of a mode space approach (either coupled or uncoupled) produces high computational efficiency that makes our 3D quantum simulator practical for extensive device simulation and design. Scattering in SNWTs is then treated by a simple model that uses so-called Buttiker probes, which was previously used in metal-oxide-semiconductor field effect transistor (MOSFET) simulations. Using this simple approach, the effects of scattering on both internal device characteristics and terminal currents can be examined, which enables our simulator to be used for the exploration of realistic performance limits of SNWTs.
Gerhard Klimeck - One of the best experts on this subject based on the ideXlab platform.
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Simulations of nanowire transistors: atomistic vs. Effective Mass models
Journal of Computational Electronics, 2008Co-Authors: Neophytos Neophytou, Mark Lundstrom, Abhijeet Paul, Gerhard KlimeckAbstract:The ballistic performance of electron transport in nanowire transistors is examined using a 10 orbital sp3d5s* atomistic tight-binding model for the description of the electronic structure, and the top-of-the-barrier semiclassical ballistic model for calculation of the transport properties of the transistors. The dispersion is self consistently computed with a 2D Poisson solution for the electrostatic potential in the cross section of the wire. The Effective Mass of the nanowire changes significantly from the bulk value under strong quantization, and effects such as valley splitting strongly lift the degeneracies of the valleys. These effects are pronounced even further under filling of the lattice with charge. The Effective Mass Approximation is in good agreement with the tight binding model in terms of current–voltage characteristics only in certain cases. In general, for small diameter wires, the Effective Mass Approximation fails.
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on the validity of the parabolic Effective Mass Approximation for the i v calculation of silicon nanowire transistors
IEEE Transactions on Electron Devices, 2005Co-Authors: Jing Wang, Anisur Rahman, Avik W Ghosh, Gerhard Klimeck, Mark LundstromAbstract:This paper examines the validity of the widely used parabolic Effective-Mass Approximation for computing the current-voltage (I-V) characteristics of silicon nanowire transistors (SNWTs). The energy dispersion relations for unrelaxed Si nanowires are first computed by using an sp/sup 3/d/sup 5/s/sup */ tight-binding (TB) model. A seminumerical ballistic field-effect transistor model is then adopted to evaluate the I-V characteristics of the (n-type) SNWTs based on both a TB dispersion relation and parabolic energy bands. In comparison with the TB approach, the parabolic Effective-Mass model with bulk Effective-Masses significantly overestimates SNWT threshold voltages when the wire width is <3 nm, and ON-currents when the wire width is <5 nm. By introducing two analytical equations with two tuning parameters, however, the Effective-Mass Approximation can well reproduce the TB I-V results even at a /spl sim/1.36-nm wire width.
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On the validity of the parabolic Effective-Mass Approximation for the I-V calculation of silicon nanowire transistors
IEEE Transactions on Electron Devices, 2005Co-Authors: Jing Wang, Anisur Rahman, Gerhard Klimeck, A. Ghosh, Mark LundstromAbstract:This paper examines the validity of the widely used parabolic Effective-Mass Approximation for computing the current-voltage (I-V) characteristics of silicon nanowire transistors (SNWTs). The energy dispersion relations for unrelaxed Si nanowires are first computed by using an sp/sup 3/d/sup 5/s/sup */ tight-binding (TB) model. A seminumerical ballistic field-effect transistor model is then adopted to evaluate the I-V characteristics of the (n-type) SNWTs based on both a TB dispersion relation and parabolic energy bands. In comparison with the TB approach, the parabolic Effective-Mass model with bulk Effective-Masses significantly overestimates SNWT threshold voltages when the wire width is
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on the validity of the parabolic Effective Mass Approximation for the current voltage calculation of silicon nanowire transistors
arXiv: Mesoscale and Nanoscale Physics, 2004Co-Authors: Jing Wang, Anisur Rahman, Avik W Ghosh, Gerhard Klimeck, Mark LundstromAbstract:This paper examines the validity of the widely-used parabolic Effective-Mass Approximation for computing the current-voltage (I-V) characteristics of silicon nanowire transistors (SNWTs). The energy dispersion relations for unrelaxed Si nanowires are first computed by using an sp3d5s* tight-binding model. A semi-numerical ballistic FET model is then adopted to evaluate the I-V characteristics of the (n-type) SNWTs based on both a tight-binding dispersion relation and parabolic energy bands. In comparison with the tight-binding approach, the parabolic Effective-Mass model with bulk Effective-Masses significantly overestimates SNWT threshold voltages when the wire width is <3nm, and ON-currents when the wire width is <5nm. By introducing two analytical equations with two tuning parameters, however, the Effective-Mass Approximation can well reproduce the tight-binding I-V results even at a \~1.36nm wire with.
Valder N. Freire - One of the best experts on this subject based on the ideXlab platform.
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Transmission in compositionally nonabrupt GaAs/AlxGa1-xAs heterojunctions: beyond the constant interfacial Effective-Mass Approximation
Superlattices and Microstructures, 1995Co-Authors: J. Ribeiro Filho, G. A. Farias, Valder N. FreireAbstract:Abstract The transmission properties of compositionally nonabrupt GaAs/AlxGa1-xAs heterojunctions are calculated by taking into account the spatial dependence of the carrier Effective Mass through the nonabrupt interface. The description of the nonabrupt heterojunctions is obtained with the assumption of a linear aluminium molar fraction variation in the interface. A multistep technique is used for the numerical solution of the Hamiltonian with a space dependent Effective Mass. The linear spatial dependence of the Effective Mass through the interface changes the transmission properties of compositionally nonabrupt GaAs/AlxGa1-xAs heterojunctions in comparison with those obtained with the constant Effective Mass Approximation. The absence of resonant peaks for large interface widths is shown for electrons and holes, in disagreement with a prior prediction of their existence.
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transmission in compositionally nonabrupt gaas alxga1 xas heterojunctions beyond the constant interfacial Effective Mass Approximation
Superlattices and Microstructures, 1995Co-Authors: Ribeiro J Filho, G. A. Farias, Valder N. FreireAbstract:Abstract The transmission properties of compositionally nonabrupt GaAs/AlxGa1-xAs heterojunctions are calculated by taking into account the spatial dependence of the carrier Effective Mass through the nonabrupt interface. The description of the nonabrupt heterojunctions is obtained with the assumption of a linear aluminium molar fraction variation in the interface. A multistep technique is used for the numerical solution of the Hamiltonian with a space dependent Effective Mass. The linear spatial dependence of the Effective Mass through the interface changes the transmission properties of compositionally nonabrupt GaAs/AlxGa1-xAs heterojunctions in comparison with those obtained with the constant Effective Mass Approximation. The absence of resonant peaks for large interface widths is shown for electrons and holes, in disagreement with a prior prediction of their existence.
V. N. Saltanov - One of the best experts on this subject based on the ideXlab platform.
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Spin-dependent transport in magnetic sandwiches in the Effective-Mass Approximation
Semiconductor physics quantum electronics and optoelectronics, 2006Co-Authors: V. F. Los, V. N. SaltanovAbstract:A theory describing a spin-dependent transport of electrons through a thin metallic (or insulator) nonmagnetic layer sandwiched between two ferromagnets is developed in the ballistic regime and current-perpendicular-to-plane (CPP) geometry. The theory is based on the Landauer formalism and the transmission amplitude for the electron Bloch waves with an arbitrary dispersion law travelling from one ferromagnet to another through a nonmagnetic spacer (metallic or insulator). The semiclassical (non- oscillating) part of the magnetoresistance ratio for a metallic spacer is considered in the Effective-Mass Approximation for the sandwich band structure. The parameters defining the value of the giant magnetoresistance (GMR) effect are obtained. It is shown that the electron specular scattering on the interfaces may be the cause for the CPP GMR effect. The influence of the electronic structure on the CPP GMR effect has been studied numerically in the Effective-Mass Approximation.
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A theory of spin-dependent ballistic transport in the Effective-Mass Approximation
Journal of Magnetism and Magnetic Materials, 2002Co-Authors: V. F. Los, V. N. SaltanovAbstract:A unified theory describing a spin-dependent transport of electrons through a thin metallic or insulator nonmagnetic layer sandwiched between two ferromagnets is developed in the ballistic regime and current-perpendicular-to-plane (CPP) geometry. The theory is based on the Landauer formalism and the exact electron transmission coefficient in the Effective-Mass Approximation. Results of numerical calculations are presented.