Pub Date : 2014-06-03DOI: 10.1109/IWCE.2014.6865819
I. Gamba
We will discuss recent development in the simulation of Boltzmann-Poisson systems and Wigner transport by deterministic numerical solvers. We have proposed to solve linear transport problems using a Discontinuous Galerkin (DG) Finite Element Method (FEM) approach that allows adaptivity and accuracy by a flexible choice of basis functions, as well as numerical efficiency by parallelization and scalability. In the case of non-linear transport, spectral methods may be competitive for the calculation of anisotropic scattering. Such numerical schemes can be competitive to DSMC methods and have the advantage of an easy and accurate implementation of boundary conditions including charge neutrality at contacts and specular and diffusive reflection at insulating and interface boundaries. These deterministic solvers are able to resolve small scales (or order 10-7 to 10-6) that DSMC approach may not be able to handle.
{"title":"Alternative computational methods for Boltzmann and Wigner models in charged transport systems","authors":"I. Gamba","doi":"10.1109/IWCE.2014.6865819","DOIUrl":"https://doi.org/10.1109/IWCE.2014.6865819","url":null,"abstract":"We will discuss recent development in the simulation of Boltzmann-Poisson systems and Wigner transport by deterministic numerical solvers. We have proposed to solve linear transport problems using a Discontinuous Galerkin (DG) Finite Element Method (FEM) approach that allows adaptivity and accuracy by a flexible choice of basis functions, as well as numerical efficiency by parallelization and scalability. In the case of non-linear transport, spectral methods may be competitive for the calculation of anisotropic scattering. Such numerical schemes can be competitive to DSMC methods and have the advantage of an easy and accurate implementation of boundary conditions including charge neutrality at contacts and specular and diffusive reflection at insulating and interface boundaries. These deterministic solvers are able to resolve small scales (or order 10-7 to 10-6) that DSMC approach may not be able to handle.","PeriodicalId":168149,"journal":{"name":"2014 International Workshop on Computational Electronics (IWCE)","volume":"70 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128363536","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-06-03DOI: 10.1109/IWCE.2014.6865846
J. Fang, W. Vandenberghe, M. Fischetti
Empirical pseudopotentials are employed to study ballistic electron transport in nanoscale open systems. The boundary conditions are treated using the complex band structure and Schrödinger equation is solved self-consistently with Poisson equation employing parallel computing technique and a sparse-matrix solver. The example of a Si NanoWire is considered.
{"title":"Full-band ballistic quantum transport in nanostructures using empirical pseudopotentials","authors":"J. Fang, W. Vandenberghe, M. Fischetti","doi":"10.1109/IWCE.2014.6865846","DOIUrl":"https://doi.org/10.1109/IWCE.2014.6865846","url":null,"abstract":"Empirical pseudopotentials are employed to study ballistic electron transport in nanoscale open systems. The boundary conditions are treated using the complex band structure and Schrödinger equation is solved self-consistently with Poisson equation employing parallel computing technique and a sparse-matrix solver. The example of a Si NanoWire is considered.","PeriodicalId":168149,"journal":{"name":"2014 International Workshop on Computational Electronics (IWCE)","volume":"51 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115958219","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-06-03DOI: 10.1109/IWCE.2014.6865835
F. Sacconi, M. Auf der Maur, A. Di Carlo, A. Pecchia
In this work we present a theoretical study of the effect of random alloy fluctuations in a InGaN inclusion embedded in a GaN nanowire (NW) LED on the electronic and optoelectronic properties. The calculations are based on an empirical tight-binding (ETB) model, while strain is calculated with a valence force field (VFF) method. Energy gaps distributions are obtained and an optical spectral broadening of the cumulative spectra is found, due to alloy fluctuations. A correlation between ground state transition energies and optical strengths has been found, with Virtual Crystal Approximation (VCA) clearly overestimating random mean results.
{"title":"Atomistic simulation of random alloy fluctuations in InGaN/GaN nanowires","authors":"F. Sacconi, M. Auf der Maur, A. Di Carlo, A. Pecchia","doi":"10.1109/IWCE.2014.6865835","DOIUrl":"https://doi.org/10.1109/IWCE.2014.6865835","url":null,"abstract":"In this work we present a theoretical study of the effect of random alloy fluctuations in a InGaN inclusion embedded in a GaN nanowire (NW) LED on the electronic and optoelectronic properties. The calculations are based on an empirical tight-binding (ETB) model, while strain is calculated with a valence force field (VFF) method. Energy gaps distributions are obtained and an optical spectral broadening of the cumulative spectra is found, due to alloy fluctuations. A correlation between ground state transition energies and optical strengths has been found, with Virtual Crystal Approximation (VCA) clearly overestimating random mean results.","PeriodicalId":168149,"journal":{"name":"2014 International Workshop on Computational Electronics (IWCE)","volume":"380 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128005518","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-06-03DOI: 10.1109/IWCE.2014.6865865
P. Marconcini, M. Macucci
We have developed a code for the simulation of graphene-based devices consisting of cascaded armchair sections with width discontinuities, in the presence of a generic potential landscape. This is based on a scattering-matrix approach and on the solution of the Dirac equation in the reciprocal space. The presence of width discontinuities requires a particular treatment of the continuity equation for the wave function on the two inequivalent sublattices. Validation has been performed via a comparison with the results of a tight-binding calculation, for a sample with a size small enough to be amenable to this latter approach. Our method can be applied to graphene devices with a size up to a few microns, which is computationally prohibitive for tight-binding techniques.
{"title":"Transport analysis of graphene-based devices with width discontinuities","authors":"P. Marconcini, M. Macucci","doi":"10.1109/IWCE.2014.6865865","DOIUrl":"https://doi.org/10.1109/IWCE.2014.6865865","url":null,"abstract":"We have developed a code for the simulation of graphene-based devices consisting of cascaded armchair sections with width discontinuities, in the presence of a generic potential landscape. This is based on a scattering-matrix approach and on the solution of the Dirac equation in the reciprocal space. The presence of width discontinuities requires a particular treatment of the continuity equation for the wave function on the two inequivalent sublattices. Validation has been performed via a comparison with the results of a tight-binding calculation, for a sample with a size small enough to be amenable to this latter approach. Our method can be applied to graphene devices with a size up to a few microns, which is computationally prohibitive for tight-binding techniques.","PeriodicalId":168149,"journal":{"name":"2014 International Workshop on Computational Electronics (IWCE)","volume":"5 5","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134192029","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-06-03DOI: 10.1109/IWCE.2014.6865838
D. Logoteta, G. Fiori, G. Iannaccone
We compare the performance prospects of three recently proposed and demonstrated transistors based on vertical and lateral graphene-based heterostructures, with the requirements of the International Technology Roadmap for Semiconductors. All devices provide large Ion/Ioff ratios, but only the lateral heterostructure field-effect transistors exhibit promising dynamic figures of merit, i.e. delay time and power-delay-product. The assessment is based on numerical simulations using our in-house nanoscale device simulation tool NanoTCAD Vides.
{"title":"Optimization and benchmarking of graphene-based heterostructure FETs","authors":"D. Logoteta, G. Fiori, G. Iannaccone","doi":"10.1109/IWCE.2014.6865838","DOIUrl":"https://doi.org/10.1109/IWCE.2014.6865838","url":null,"abstract":"We compare the performance prospects of three recently proposed and demonstrated transistors based on vertical and lateral graphene-based heterostructures, with the requirements of the International Technology Roadmap for Semiconductors. All devices provide large Ion/Ioff ratios, but only the lateral heterostructure field-effect transistors exhibit promising dynamic figures of merit, i.e. delay time and power-delay-product. The assessment is based on numerical simulations using our in-house nanoscale device simulation tool NanoTCAD Vides.","PeriodicalId":168149,"journal":{"name":"2014 International Workshop on Computational Electronics (IWCE)","volume":"66 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124245383","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-06-03DOI: 10.1109/IWCE.2014.6865814
G. Csaba, Á. Papp, W. Porod
It is widely believed that the established route of microelectronic scaling is approaching its end: further downscaling of semiconductor devices carries disproportionate penalties in power consumption and poses fundamental fabrication challenges. Instead of scaling of devices, Moore's law is now increasingly about scaling computing systems: single-core devices toward larger, multi-core systems. While there are known programming methodologies for parallelizing program codes to a few threads, only very few, special-purpose applications lend themselves to parallelization on very large numbers of cores. This motivates our quest for studying computing paradigms and algorithms that are inherently parallel [1]. Holographic / optical computing is a perfect example of such algorithms: the results of a computation are given by an interference pattern formation of many light rays (see Fig. 1 for an illustration [1]). Optical systems are impractical to realize on-chip. For this reason, we explore routes to design holographic algorithms that can be naturally integrated with microelectronic technologies and require no optical hardware. Two approaches will be discussed in this paper.
{"title":"Holographic algorithms for on-chip, non-boolean computing","authors":"G. Csaba, Á. Papp, W. Porod","doi":"10.1109/IWCE.2014.6865814","DOIUrl":"https://doi.org/10.1109/IWCE.2014.6865814","url":null,"abstract":"It is widely believed that the established route of microelectronic scaling is approaching its end: further downscaling of semiconductor devices carries disproportionate penalties in power consumption and poses fundamental fabrication challenges. Instead of scaling of devices, Moore's law is now increasingly about scaling computing systems: single-core devices toward larger, multi-core systems. While there are known programming methodologies for parallelizing program codes to a few threads, only very few, special-purpose applications lend themselves to parallelization on very large numbers of cores. This motivates our quest for studying computing paradigms and algorithms that are inherently parallel [1]. Holographic / optical computing is a perfect example of such algorithms: the results of a computation are given by an interference pattern formation of many light rays (see Fig. 1 for an illustration [1]). Optical systems are impractical to realize on-chip. For this reason, we explore routes to design holographic algorithms that can be naturally integrated with microelectronic technologies and require no optical hardware. Two approaches will be discussed in this paper.","PeriodicalId":168149,"journal":{"name":"2014 International Workshop on Computational Electronics (IWCE)","volume":"29 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125138536","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-06-03DOI: 10.1109/IWCE.2014.6865879
Kevin Haughan, M. Niemier, W. Porod, G. Csaba
This paper demonstrates Cellular Automata (CA) designs from out of plane Nanomagnetic Logic (NML). We show that the regular, low-interconnection structure of CAs enables magnetologic designs, where the beneficial characteristics of NML devices (compact, low power operation) can be fully exploited. We also demonstrate how CA rules can be modified to result in fabrication-friendly NML layouts.
{"title":"Cellular Automata designs for out of plane Nanomagnet Logic","authors":"Kevin Haughan, M. Niemier, W. Porod, G. Csaba","doi":"10.1109/IWCE.2014.6865879","DOIUrl":"https://doi.org/10.1109/IWCE.2014.6865879","url":null,"abstract":"This paper demonstrates Cellular Automata (CA) designs from out of plane Nanomagnetic Logic (NML). We show that the regular, low-interconnection structure of CAs enables magnetologic designs, where the beneficial characteristics of NML devices (compact, low power operation) can be fully exploited. We also demonstrate how CA rules can be modified to result in fabrication-friendly NML layouts.","PeriodicalId":168149,"journal":{"name":"2014 International Workshop on Computational Electronics (IWCE)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129761004","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-06-03DOI: 10.1109/IWCE.2014.6865859
A. Mahi, A. Belghachi, H. Marinchio, C. Palermo, L. Varani
By means of a numerical hydrodynamic (HD) model coupled with Poisson pseudo-2D equation, we simulate the drain current response of a high electron mobility transistor (HEMT) to a THz signal applied to its gate and/or to its drain contacts in order to obtain the optimal configuration in terms of detection.
{"title":"Simulation of plasma oscillation response to THz radiation applied upon high electron mobility transistors","authors":"A. Mahi, A. Belghachi, H. Marinchio, C. Palermo, L. Varani","doi":"10.1109/IWCE.2014.6865859","DOIUrl":"https://doi.org/10.1109/IWCE.2014.6865859","url":null,"abstract":"By means of a numerical hydrodynamic (HD) model coupled with Poisson pseudo-2D equation, we simulate the drain current response of a high electron mobility transistor (HEMT) to a THz signal applied to its gate and/or to its drain contacts in order to obtain the optimal configuration in terms of detection.","PeriodicalId":168149,"journal":{"name":"2014 International Workshop on Computational Electronics (IWCE)","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129804327","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-06-03DOI: 10.1109/IWCE.2014.6865850
Z. Zhan, F. Traversa, X. Oriols
A novel algorithm for a reduction of the computational burden associated to the time-dependent simulation of quantum transport with pure states is presented. The algorithm is based on using the superposition principle and the analytical knowledge of the free time-evolution of an initial state outside of the active region, together with absorbing layers. It is specially suited to study (many-particle and high-frequency effects) quantum transport, but it can also be applied to any other research field where the initial time-dependent pure state is located outside of the active region. Numerical results for a 1D system with the shortest simulation box imply a reduction of the computational burden of more than one order of magnitude with a negligible error.
{"title":"The shortest simulation-box for time-dependent computation of wave packets in open system","authors":"Z. Zhan, F. Traversa, X. Oriols","doi":"10.1109/IWCE.2014.6865850","DOIUrl":"https://doi.org/10.1109/IWCE.2014.6865850","url":null,"abstract":"A novel algorithm for a reduction of the computational burden associated to the time-dependent simulation of quantum transport with pure states is presented. The algorithm is based on using the superposition principle and the analytical knowledge of the free time-evolution of an initial state outside of the active region, together with absorbing layers. It is specially suited to study (many-particle and high-frequency effects) quantum transport, but it can also be applied to any other research field where the initial time-dependent pure state is located outside of the active region. Numerical results for a 1D system with the shortest simulation box imply a reduction of the computational burden of more than one order of magnitude with a negligible error.","PeriodicalId":168149,"journal":{"name":"2014 International Workshop on Computational Electronics (IWCE)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128219574","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-06-03DOI: 10.1109/IWCE.2014.6865869
V. Tran, J. Saint-Martin, P. Dollfus
By means of atomistic Tight Binding simulations, we study heterostructures made of an armchair BN nanoribbon sided by two armchair graphene ribbons where a high band gap can be opened. We show that this band gap can be significantly suppressed by applying a relatively weak transverse electric field. This effect can be used to strongly enhance the on/off current ratio higher in graphene transistors.
{"title":"Modulation of bandgap and current in Graphene/BN heterostructures by tuning the transverse electric field","authors":"V. Tran, J. Saint-Martin, P. Dollfus","doi":"10.1109/IWCE.2014.6865869","DOIUrl":"https://doi.org/10.1109/IWCE.2014.6865869","url":null,"abstract":"By means of atomistic Tight Binding simulations, we study heterostructures made of an armchair BN nanoribbon sided by two armchair graphene ribbons where a high band gap can be opened. We show that this band gap can be significantly suppressed by applying a relatively weak transverse electric field. This effect can be used to strongly enhance the on/off current ratio higher in graphene transistors.","PeriodicalId":168149,"journal":{"name":"2014 International Workshop on Computational Electronics (IWCE)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114478226","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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