Pub Date : 2012-05-22DOI: 10.1109/IWCE.2012.6242844
P. Marconcini, A. Cresti, F. Triozon, G. Fiori, B. Biel, Y. Niquet, M. Macucci, S. Roche
One of the main drawbacks of undoped graphene for digital electronics applications is its am-bipolar behavior. Here we study the trasfer characteristics of transistors based on boron-doped graphene nanoribbons with atomic concentrations up to 0.6%, showing that the presence of doping generates a clear electron-hole transport asymmetry. In order to obtain these results, we introduce a method to accurately reproduce density functional theory (DFT) results using a selfconsistent tight-binding (TB) model with a proper distribution of fixed charges.
{"title":"Electron-hole transport asymmetry in boron-doped graphene field effect transistors","authors":"P. Marconcini, A. Cresti, F. Triozon, G. Fiori, B. Biel, Y. Niquet, M. Macucci, S. Roche","doi":"10.1109/IWCE.2012.6242844","DOIUrl":"https://doi.org/10.1109/IWCE.2012.6242844","url":null,"abstract":"One of the main drawbacks of undoped graphene for digital electronics applications is its am-bipolar behavior. Here we study the trasfer characteristics of transistors based on boron-doped graphene nanoribbons with atomic concentrations up to 0.6%, showing that the presence of doping generates a clear electron-hole transport asymmetry. In order to obtain these results, we introduce a method to accurately reproduce density functional theory (DFT) results using a selfconsistent tight-binding (TB) model with a proper distribution of fixed charges.","PeriodicalId":375453,"journal":{"name":"2012 15th International Workshop on Computational Electronics","volume":"21 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-05-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114136515","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 : 2012-05-22DOI: 10.1109/IWCE.2012.6242830
S. Farid, M. Purahmad, M. Stroscio, M. Dutta
Computational analysis on the emission properties of ZnO nano wires (NWs) and coreshell quantum dots (QDs) have been made by considering the effects of scattering mechanism of the incident field and the total electric field from the surface of varied substrates. Simulation results indicate that the substrate (GaAs) having the highest emission intensity showed maximum light scattering from its surface while ITO that has the least emission intensity results in minimum rate of energy that is transferred per unit area. The simulation results proved that emission intensities spectrum is dependent on the type of substrate being used as well as the scattering of light from the surface of substrates and is independent on the type of material being deposited as well as the total electric field from the surface of substrate.
{"title":"Computational analysis on the emission of ZnO nanowires and coreshell CdSe/ZnS quantum dots deposited on different substrates","authors":"S. Farid, M. Purahmad, M. Stroscio, M. Dutta","doi":"10.1109/IWCE.2012.6242830","DOIUrl":"https://doi.org/10.1109/IWCE.2012.6242830","url":null,"abstract":"Computational analysis on the emission properties of ZnO nano wires (NWs) and coreshell quantum dots (QDs) have been made by considering the effects of scattering mechanism of the incident field and the total electric field from the surface of varied substrates. Simulation results indicate that the substrate (GaAs) having the highest emission intensity showed maximum light scattering from its surface while ITO that has the least emission intensity results in minimum rate of energy that is transferred per unit area. The simulation results proved that emission intensities spectrum is dependent on the type of substrate being used as well as the scattering of light from the surface of substrates and is independent on the type of material being deposited as well as the total electric field from the surface of substrate.","PeriodicalId":375453,"journal":{"name":"2012 15th International Workshop on Computational Electronics","volume":"53 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-05-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116702334","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 : 2012-05-22DOI: 10.1109/IWCE.2012.6242829
J. Dura, F. Triozon, D. Munteanu, S. Barraud, S. Martinie, J. Autran
This paper presents the study of electron mobility in intrinsic silicon nanowires using the Kubo-Greenwood approach. This architecture (now considered as a realistic technology [1,2]) is aimed for ultra-scaled devices up to technology nodes sub-11nm [3] with silicon films of some nanometers. At these dimensions, the transport regime is completely modified due to the multi-subband transport. However, the promising potentialities of nanowires for microelectronic applications are not still demonstrated at all simulation levels (from atomistic to circuit performances). That is why the electronic transport is here investigated numerically using the Kubo-Greenwood approach coupled to a selfconsistent Schrödinger-Poisson solver. Then, to support compact modelling including ultimate physical phenomena, an analytical model of the electron mobility and backscattering coefficient is exposed. The geometry dependence is essentially pointed out on the backscattering coefficient for a wide range of channel lengths (up to 10 nm) and diameters (3 nm≤Ø≤20 nm).
{"title":"Electronic transport in GAA silicon nanowire MOSFETs: From Kubo-Greenwood mobility including screening remote coulomb scattering to analytical backscattering coefficient","authors":"J. Dura, F. Triozon, D. Munteanu, S. Barraud, S. Martinie, J. Autran","doi":"10.1109/IWCE.2012.6242829","DOIUrl":"https://doi.org/10.1109/IWCE.2012.6242829","url":null,"abstract":"This paper presents the study of electron mobility in intrinsic silicon nanowires using the Kubo-Greenwood approach. This architecture (now considered as a realistic technology [1,2]) is aimed for ultra-scaled devices up to technology nodes sub-11nm [3] with silicon films of some nanometers. At these dimensions, the transport regime is completely modified due to the multi-subband transport. However, the promising potentialities of nanowires for microelectronic applications are not still demonstrated at all simulation levels (from atomistic to circuit performances). That is why the electronic transport is here investigated numerically using the Kubo-Greenwood approach coupled to a selfconsistent Schrödinger-Poisson solver. Then, to support compact modelling including ultimate physical phenomena, an analytical model of the electron mobility and backscattering coefficient is exposed. The geometry dependence is essentially pointed out on the backscattering coefficient for a wide range of channel lengths (up to 10 nm) and diameters (3 nm≤Ø≤20 nm).","PeriodicalId":375453,"journal":{"name":"2012 15th International Workshop on Computational Electronics","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-05-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116105864","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 : 2012-05-22DOI: 10.1109/IWCE.2012.6242819
A. Ajoy
Band-to-band tunneling (BTBT) determines the on-current in tunnel FETs (TFETs). There is a need to review and recalibrate BTBT models used in TCAD tools, which were developed when BTBT was essentially a leakage phenomenon. Here, we consider the process of BTBT through staggered heterojunctions which find application in the design of TFETs having high on-currents. We use a simple 1-D system and compare the estimates of BTBT computed with a semi-classical WKB approach and that obtained from a solution of Schrödinger's equation by a wavefunction matching procedure. We show that the WKB method significantly overestimates the tunneling current through heterojunctions.
{"title":"Band to band tunneling in heterojunctions: Semi-classical versus quantum computation","authors":"A. Ajoy","doi":"10.1109/IWCE.2012.6242819","DOIUrl":"https://doi.org/10.1109/IWCE.2012.6242819","url":null,"abstract":"Band-to-band tunneling (BTBT) determines the on-current in tunnel FETs (TFETs). There is a need to review and recalibrate BTBT models used in TCAD tools, which were developed when BTBT was essentially a leakage phenomenon. Here, we consider the process of BTBT through staggered heterojunctions which find application in the design of TFETs having high on-currents. We use a simple 1-D system and compare the estimates of BTBT computed with a semi-classical WKB approach and that obtained from a solution of Schrödinger's equation by a wavefunction matching procedure. We show that the WKB method significantly overestimates the tunneling current through heterojunctions.","PeriodicalId":375453,"journal":{"name":"2012 15th International Workshop on Computational Electronics","volume":"28 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-05-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130743728","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 : 2012-05-22DOI: 10.1109/IWCE.2012.6242828
V. Talbo, S. Galdin-Retailleau, D. Querlioz, P. Dollfus
The 3D Monte Carlo simulation of an Si dot-based double-tunnel junction shows not only the possibility of shot noise suppression down to the Fano factor of 0.5, but also of super-Poissonian noise in the case of multi-state process. The counting statistics of the tunneling events provides a clear interpretation of the different noise regimes according to the balance between the different tunneling rates involved.
{"title":"Shot noise behavior in single-electron quantum dot-based structures","authors":"V. Talbo, S. Galdin-Retailleau, D. Querlioz, P. Dollfus","doi":"10.1109/IWCE.2012.6242828","DOIUrl":"https://doi.org/10.1109/IWCE.2012.6242828","url":null,"abstract":"The 3D Monte Carlo simulation of an Si dot-based double-tunnel junction shows not only the possibility of shot noise suppression down to the Fano factor of 0.5, but also of super-Poissonian noise in the case of multi-state process. The counting statistics of the tunneling events provides a clear interpretation of the different noise regimes according to the balance between the different tunneling rates involved.","PeriodicalId":375453,"journal":{"name":"2012 15th International Workshop on Computational Electronics","volume":"19 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-05-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131413195","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 : 2012-05-22DOI: 10.1109/IWCE.2012.6242864
S. Sundaresan, K. Yalavarthi, S. Ahmed
Single-particle electronic structure and optical transition rates between the HOMO and LUMO states of a self-organized wurtzite GaN/AlN single quantum dot grown along the [0001] axis are calculated within an atomistic 20-band sp3 d5 s* tight-binding framework. The GaN/AlN quantum dot used in this computational study is realistically-sized (containing ~9 million atoms) and of truncated pyramid shape having height and base length of 4.5 nm and 23 nm, respectively. These reduced-dimensionality III-N structures are subject to competing effects of size-quantization and long-range internal fields that originate from: a) fundamental crystal atomicity and the interface discontinuity between two dissimilar materials; b) atomistically strained active region; c) strain-induced piezoelectricity; and d) spontaneous polarization (pyroelectricity). The mechano-electrical internal fields in the structure have been modeled using a combination of an atomistic valence force-field molecular mechanics (VFF MM) approach and a three-dimensional Poisson solver, and have found to strongly modulate the intrinsic single-particle electronic and optical properties of the quantum dots. In particular, in contrast to the well-studied InN/GaN systems, the effects of piezoelectric and pyroelectric fields add up (peak pyroelectric potential being larger than the piezoelectric counterpart) and result in a large redshift in the electronic bandgap near the Brillouin zone center (known as quantum confined stark effect), pronounced non-degeneracy in the excited states, strongly suppressed optical transition (increased recombination time), and anisotropic emission spectra.
{"title":"Effects of atomicity and internal polarization on the electronic and optical properties of GaN/AlN quantum dots: Multimillion-atom coupled VFF MM-sp3 d5 s∗ tight-binding simulations","authors":"S. Sundaresan, K. Yalavarthi, S. Ahmed","doi":"10.1109/IWCE.2012.6242864","DOIUrl":"https://doi.org/10.1109/IWCE.2012.6242864","url":null,"abstract":"Single-particle electronic structure and optical transition rates between the HOMO and LUMO states of a self-organized wurtzite GaN/AlN single quantum dot grown along the [0001] axis are calculated within an atomistic 20-band sp3 d5 s* tight-binding framework. The GaN/AlN quantum dot used in this computational study is realistically-sized (containing ~9 million atoms) and of truncated pyramid shape having height and base length of 4.5 nm and 23 nm, respectively. These reduced-dimensionality III-N structures are subject to competing effects of size-quantization and long-range internal fields that originate from: a) fundamental crystal atomicity and the interface discontinuity between two dissimilar materials; b) atomistically strained active region; c) strain-induced piezoelectricity; and d) spontaneous polarization (pyroelectricity). The mechano-electrical internal fields in the structure have been modeled using a combination of an atomistic valence force-field molecular mechanics (VFF MM) approach and a three-dimensional Poisson solver, and have found to strongly modulate the intrinsic single-particle electronic and optical properties of the quantum dots. In particular, in contrast to the well-studied InN/GaN systems, the effects of piezoelectric and pyroelectric fields add up (peak pyroelectric potential being larger than the piezoelectric counterpart) and result in a large redshift in the electronic bandgap near the Brillouin zone center (known as quantum confined stark effect), pronounced non-degeneracy in the excited states, strongly suppressed optical transition (increased recombination time), and anisotropic emission spectra.","PeriodicalId":375453,"journal":{"name":"2012 15th International Workshop on Computational Electronics","volume":"2018 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-05-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126784883","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 : 2012-05-22DOI: 10.1109/IWCE.2012.6242824
M. Auf der Maur, G. Romano, A. Di Carlo
A fully selfconsistent, coupled electro-thermo-mechanical model for nitride-based devices is presented and applied to a high-power AlGaN/GaN High Electron Mobility Transistor (HEMT). The influence of converse piezoelectric effect, thermal stress and of the selfconsistent coupling on the static device characteristics and on the stress distribution in the device is studied.
{"title":"Electro-thermo-mechanical simulation of AlGaN/GaN HEMTs","authors":"M. Auf der Maur, G. Romano, A. Di Carlo","doi":"10.1109/IWCE.2012.6242824","DOIUrl":"https://doi.org/10.1109/IWCE.2012.6242824","url":null,"abstract":"A fully selfconsistent, coupled electro-thermo-mechanical model for nitride-based devices is presented and applied to a high-power AlGaN/GaN High Electron Mobility Transistor (HEMT). The influence of converse piezoelectric effect, thermal stress and of the selfconsistent coupling on the static device characteristics and on the stress distribution in the device is studied.","PeriodicalId":375453,"journal":{"name":"2012 15th International Workshop on Computational Electronics","volume":"36 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-05-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123141588","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 : 2012-05-22DOI: 10.1109/IWCE.2012.6242834
M. Grupen
Progress on a Fermi kinetics hot electron transport model, a numerically efficient approach based on ideal Fermi gas thermodynamics, is reported. The basics of the model are first reviewed, and then methods for incorporating ionized impurity, acoustic phonon, and long range electron-electron scattering are described. The different roles the various scattering mechanisms serve within the model and their effects on simulation results are also presented.
{"title":"Scattering in GaAs for Fermi kinetics transport","authors":"M. Grupen","doi":"10.1109/IWCE.2012.6242834","DOIUrl":"https://doi.org/10.1109/IWCE.2012.6242834","url":null,"abstract":"Progress on a Fermi kinetics hot electron transport model, a numerically efficient approach based on ideal Fermi gas thermodynamics, is reported. The basics of the model are first reviewed, and then methods for incorporating ionized impurity, acoustic phonon, and long range electron-electron scattering are described. The different roles the various scattering mechanisms serve within the model and their effects on simulation results are also presented.","PeriodicalId":375453,"journal":{"name":"2012 15th International Workshop on Computational Electronics","volume":"17 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-05-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116853507","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 : 2012-05-22DOI: 10.1109/IWCE.2012.6242826
T. Boykin, M. Luisier, N. Kharche, X. Jaing, S. Nayak, A. Martini, Gerhard Klimeck
The single π-orbital model for graphene has been successful for extended, perfectly flat sheets. However, it cannot model hydrogen passivation, multi-layer structures, or rippled sheets. We address these shortcomings by adding a full complement of d-orbitals to the traditional {s, p} set. To model strain behavior and multi-layer structures we fit scaling exponents and introduce a long-range scaling modulation function. We apply the model to rippled graphene nanoribbons and bilayer graphene sheets.
{"title":"Multiband tight-binding model for strained and bilayer graphene from DFT calculations","authors":"T. Boykin, M. Luisier, N. Kharche, X. Jaing, S. Nayak, A. Martini, Gerhard Klimeck","doi":"10.1109/IWCE.2012.6242826","DOIUrl":"https://doi.org/10.1109/IWCE.2012.6242826","url":null,"abstract":"The single π-orbital model for graphene has been successful for extended, perfectly flat sheets. However, it cannot model hydrogen passivation, multi-layer structures, or rippled sheets. We address these shortcomings by adding a full complement of d-orbitals to the traditional {s, p} set. To model strain behavior and multi-layer structures we fit scaling exponents and introduce a long-range scaling modulation function. We apply the model to rippled graphene nanoribbons and bilayer graphene sheets.","PeriodicalId":375453,"journal":{"name":"2012 15th International Workshop on Computational Electronics","volume":"65 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-05-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124205152","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 : 2012-05-22DOI: 10.1109/IWCE.2012.6242849
X. Oriols, F. Traversa, G. Albareda, A. Benali, A. Alarcón, S. Yaro, X. Cartoixà
With the aim of manufacturing faster and smaller devices, the electronic industry is today entering into the nanoscale and the high frequency regimes. In this particular scenario, the dynamics of the electron charge becomes affected by quantum mechanical laws, both, for its spatial or temporal description. We have recently shown that Bohmian trajectories allow a direct treatment of the time-dependent many-particle interaction among electrons with an accuracy comparable to Density Functional Theory techniques. In addition, Bohmian mechanics, by combining wave functions and trajectories, provides a very simple description on how to describe multi-time measurements in quantum scenarios. Using the previous formalism, in this work we present a general purpose time-dependent 3D quantum electron transport simulator named BITLLES (Bohmian Interacting Transport in large low-dimensional Electronic Structures) especially indicated for AC, transients and noise predictions. As a numerical example of its capabilities, we compute the full electrical characteristics (DC, High frequency and fluctuations) of a Resonant Tunneling Diode.
{"title":"Multi-time measurement and displacement current in time-dependent quantum transport","authors":"X. Oriols, F. Traversa, G. Albareda, A. Benali, A. Alarcón, S. Yaro, X. Cartoixà","doi":"10.1109/IWCE.2012.6242849","DOIUrl":"https://doi.org/10.1109/IWCE.2012.6242849","url":null,"abstract":"With the aim of manufacturing faster and smaller devices, the electronic industry is today entering into the nanoscale and the high frequency regimes. In this particular scenario, the dynamics of the electron charge becomes affected by quantum mechanical laws, both, for its spatial or temporal description. We have recently shown that Bohmian trajectories allow a direct treatment of the time-dependent many-particle interaction among electrons with an accuracy comparable to Density Functional Theory techniques. In addition, Bohmian mechanics, by combining wave functions and trajectories, provides a very simple description on how to describe multi-time measurements in quantum scenarios. Using the previous formalism, in this work we present a general purpose time-dependent 3D quantum electron transport simulator named BITLLES (Bohmian Interacting Transport in large low-dimensional Electronic Structures) especially indicated for AC, transients and noise predictions. As a numerical example of its capabilities, we compute the full electrical characteristics (DC, High frequency and fluctuations) of a Resonant Tunneling Diode.","PeriodicalId":375453,"journal":{"name":"2012 15th International Workshop on Computational Electronics","volume":"75 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-05-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122827195","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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