A. García-Barrientos, F. Coyotl-Mixcoatl, V. Grimalsky
A Numerical study of amplification of space charge waves (SCW) due to the negative differential conductivity in n-GaN films placed onto a semi-infinite substrate is investigated. A case of transverse non-uniform film is considered. The set of balance equations for concentration, drift velocity, and the averaged energy to describe the dynamics of space charge waves were used jointly with the Poisson equation for the electric field. It is possible to observe an amplification of SCW in n-GaN films of submicron thicknesses at essentially higher frequencies f >;100 GHz, when compared with n-GaAs. Two-dimensional simulation of spatial distribution of the alternative part of the electric field of space charge wave in 2D is presented.
{"title":"A numerical study of amplification of space charge waves in n-GaN films","authors":"A. García-Barrientos, F. Coyotl-Mixcoatl, V. Grimalsky","doi":"10.5772/47764","DOIUrl":"https://doi.org/10.5772/47764","url":null,"abstract":"A Numerical study of amplification of space charge waves (SCW) due to the negative differential conductivity in n-GaN films placed onto a semi-infinite substrate is investigated. A case of transverse non-uniform film is considered. The set of balance equations for concentration, drift velocity, and the averaged energy to describe the dynamics of space charge waves were used jointly with the Poisson equation for the electric field. It is possible to observe an amplification of SCW in n-GaN films of submicron thicknesses at essentially higher frequencies f >;100 GHz, when compared with n-GaAs. Two-dimensional simulation of spatial distribution of the alternative part of the electric field of space charge wave in 2D is presented.","PeriodicalId":375453,"journal":{"name":"2012 15th International Workshop on Computational Electronics","volume":"103 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":"124007844","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.2012.6242832
X. Gao, E. Nielsen, R. Muller, R. Young, A. Salinger, N. Bishop, M. Carroll
We present the Quantum Computer Aided Design (QCAD) simulator that targets modeling quantum devices, particularly Si double quantum dots (DQDs) developed for quantum computing. The simulator core includes Poisson, Schrodinger, and Configuration Interaction solvers which can be run individually or combined self-consistently. The simulator is built upon Sandia-developed Trilinos and Albany components, and is interfaced with the Dakota optimization tool. It is being developed for seamless integration, high flexibility and throughput, and is intended to be open source. The QCAD tool has been used to simulate a large number of fabricated silicon DQDs and has provided fast feedback for design comparison and optimization.
{"title":"The QCAD framework for quantum device modeling","authors":"X. Gao, E. Nielsen, R. Muller, R. Young, A. Salinger, N. Bishop, M. Carroll","doi":"10.1109/IWCE.2012.6242832","DOIUrl":"https://doi.org/10.1109/IWCE.2012.6242832","url":null,"abstract":"We present the Quantum Computer Aided Design (QCAD) simulator that targets modeling quantum devices, particularly Si double quantum dots (DQDs) developed for quantum computing. The simulator core includes Poisson, Schrodinger, and Configuration Interaction solvers which can be run individually or combined self-consistently. The simulator is built upon Sandia-developed Trilinos and Albany components, and is interfaced with the Dakota optimization tool. It is being developed for seamless integration, high flexibility and throughput, and is intended to be open source. The QCAD tool has been used to simulate a large number of fabricated silicon DQDs and has provided fast feedback for design comparison and optimization.","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":"130016161","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.2012.6242841
D. Logoteta, P. Marconcini, M. Connolly, Charles G. Smith, M. Macucci
We propose a model for the numerical simulation of a two-terminal scanning gate spectroscopy experiment on bilayer graphene in the Quantum Hall regime. We start from the Chalker-Coddington random network model and link the model parameters with some of the relevant quantities in the experimental setup. The comparison between the simulation and the measurement results show a good qualitative and in several ways, quantitative agreement.
{"title":"Numerical simulation of scanning gate spectroscopy in bilayer graphene in the Quantum Hall regime","authors":"D. Logoteta, P. Marconcini, M. Connolly, Charles G. Smith, M. Macucci","doi":"10.1109/IWCE.2012.6242841","DOIUrl":"https://doi.org/10.1109/IWCE.2012.6242841","url":null,"abstract":"We propose a model for the numerical simulation of a two-terminal scanning gate spectroscopy experiment on bilayer graphene in the Quantum Hall regime. We start from the Chalker-Coddington random network model and link the model parameters with some of the relevant quantities in the experimental setup. The comparison between the simulation and the measurement results show a good qualitative and in several ways, quantitative agreement.","PeriodicalId":375453,"journal":{"name":"2012 15th International Workshop on Computational Electronics","volume":"76 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":"134220965","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.2012.6242823
S. Amoroso, F. Adamu-Lema, S. Markov, L. Gerrer, A. Asenov
In this work we present a 3D dynamic simulation analysis for the reliability evaluation of a decananometer MOSFET device. We have focused our attention on the Random Telegraph Noise (RTN) phenomenon, showing that the statistical variability induced by the discrete nature of matter and charge has a fundamental impact on the reliability performance of nanoscale devices, in both transient and steady-state operating regimes.
{"title":"3D dynamic RTN simulation of a 25nm MOSFET: The importance of variability in reliability evaluation of decananometer devices","authors":"S. Amoroso, F. Adamu-Lema, S. Markov, L. Gerrer, A. Asenov","doi":"10.1109/IWCE.2012.6242823","DOIUrl":"https://doi.org/10.1109/IWCE.2012.6242823","url":null,"abstract":"In this work we present a 3D dynamic simulation analysis for the reliability evaluation of a decananometer MOSFET device. We have focused our attention on the Random Telegraph Noise (RTN) phenomenon, showing that the statistical variability induced by the discrete nature of matter and charge has a fundamental impact on the reliability performance of nanoscale devices, in both transient and steady-state operating regimes.","PeriodicalId":375453,"journal":{"name":"2012 15th International Workshop on Computational Electronics","volume":"61 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":"134315759","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.2012.6242867
J. Weinbub, K. Rupp, L. Filipovic, A. Makarov, S. Selberherr
We present an approach for implementing open source simulation tools in the field of semiconductor device and process simulation based on our execution framework ViennaX. We apply a modular concept, where functionality is separated into plugins, which in turn can be combined to form full-fledged simulation tools by utilizing ViennaX's task graph approach. Due to the applied plugin concept, a high degree of flexibility is introduced, as components can be easily exchanged. Simulation results are shown, depicting the applicability of our approach for different tools.
{"title":"Towards a free open source process and device simulation framework","authors":"J. Weinbub, K. Rupp, L. Filipovic, A. Makarov, S. Selberherr","doi":"10.1109/IWCE.2012.6242867","DOIUrl":"https://doi.org/10.1109/IWCE.2012.6242867","url":null,"abstract":"We present an approach for implementing open source simulation tools in the field of semiconductor device and process simulation based on our execution framework ViennaX. We apply a modular concept, where functionality is separated into plugins, which in turn can be combined to form full-fledged simulation tools by utilizing ViennaX's task graph approach. Due to the applied plugin concept, a high degree of flexibility is introduced, as components can be easily exchanged. Simulation results are shown, depicting the applicability of our approach for different tools.","PeriodicalId":375453,"journal":{"name":"2012 15th International Workshop on Computational Electronics","volume":"38 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":"132428761","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.2012.6242854
M. Purahmad, M. Stroscio, M. Dutta
We have investigated the effect of piezoelectric charges on the surface depletion region of ZnO NWs. By considering an inner region with a non-negligible density of free carriers and a depleted region at surface of the ZnO NWs and by solving the Poisson equation in the depleted region, the surface depletion width is derived. Thus, the effect of piezoelectric charges on the surface depletion region has been investigated.
{"title":"A numerical analysis on the effect of piezoelectric charges on the surface depletion layer of ZnO nanowires","authors":"M. Purahmad, M. Stroscio, M. Dutta","doi":"10.1109/IWCE.2012.6242854","DOIUrl":"https://doi.org/10.1109/IWCE.2012.6242854","url":null,"abstract":"We have investigated the effect of piezoelectric charges on the surface depletion region of ZnO NWs. By considering an inner region with a non-negligible density of free carriers and a depleted region at surface of the ZnO NWs and by solving the Poisson equation in the depleted region, the surface depletion width is derived. Thus, the effect of piezoelectric charges on the surface depletion region has been investigated.","PeriodicalId":375453,"journal":{"name":"2012 15th International Workshop on Computational Electronics","volume":"56 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":"132278290","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.2012.6242835
T. Gunst, Jing-Tao Lu, T. Markussen, A. Jauho, M. Brandbyge
We calculate the electronic and thermal transport properties of devices based on finite graphene antidot lattices (GALs) connected to perfect graphene leads. We use an atomistic approach based on the π-tight-binding model, the Brenner potential, and employing recursive Green's functions. We consider the effect of random disorder on the electronic and thermal transport properties, and examine the potential gain of thermoelectric merit by tailoring of the disorder. We propose several routes to optimize the transport properties of the GAL systems. Finally, we illustrate how quantum thermal transport can be addressed by molecular dynamics simulations, and compare to the Green's function results for the GAL systems in the ballistic limit.
{"title":"Thermoelectric properties of disordered graphene antidot devices","authors":"T. Gunst, Jing-Tao Lu, T. Markussen, A. Jauho, M. Brandbyge","doi":"10.1109/IWCE.2012.6242835","DOIUrl":"https://doi.org/10.1109/IWCE.2012.6242835","url":null,"abstract":"We calculate the electronic and thermal transport properties of devices based on finite graphene antidot lattices (GALs) connected to perfect graphene leads. We use an atomistic approach based on the π-tight-binding model, the Brenner potential, and employing recursive Green's functions. We consider the effect of random disorder on the electronic and thermal transport properties, and examine the potential gain of thermoelectric merit by tailoring of the disorder. We propose several routes to optimize the transport properties of the GAL systems. Finally, we illustrate how quantum thermal transport can be addressed by molecular dynamics simulations, and compare to the Green's function results for the GAL systems in the ballistic limit.","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":"114197734","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.2012.6242859
B. Savoie, S. Tan, J. Jerome, C. Shu, M. Ratner, T. Marks
In the past decade, organic photovoltaics (OPV) have emerged as an intensely studied alternative energy technology. The OPV platform presents several attractive qualities, yet, the high disorder and relative low mobility of the materials comprising OPV systems remain a bottleneck to further progress. We report here a modeling methodology that quantifies the efficiency losses engendered by the low mobility of these systems. We also report a methodology that explicitly treats the charge transfer (CT) state that has been shown to influence device performance. We compare two commonly studied OPV architectures, the bilayer (BL) and blended bulk-heterojunction (BHJ), and separately investigate the sensitivity of each architecture to mobility. Our findings suggest that mismatched mobilities of the active layer components can lead to additional recombination currents. We find that the collection current is largely limited by the slow carrier; consequently, the high mobility carriers only increase the recombination current without aiding collection.
{"title":"Ascertaining the limitations of low mobility on organic solar cell performance","authors":"B. Savoie, S. Tan, J. Jerome, C. Shu, M. Ratner, T. Marks","doi":"10.1109/IWCE.2012.6242859","DOIUrl":"https://doi.org/10.1109/IWCE.2012.6242859","url":null,"abstract":"In the past decade, organic photovoltaics (OPV) have emerged as an intensely studied alternative energy technology. The OPV platform presents several attractive qualities, yet, the high disorder and relative low mobility of the materials comprising OPV systems remain a bottleneck to further progress. We report here a modeling methodology that quantifies the efficiency losses engendered by the low mobility of these systems. We also report a methodology that explicitly treats the charge transfer (CT) state that has been shown to influence device performance. We compare two commonly studied OPV architectures, the bilayer (BL) and blended bulk-heterojunction (BHJ), and separately investigate the sensitivity of each architecture to mobility. Our findings suggest that mismatched mobilities of the active layer components can lead to additional recombination currents. We find that the collection current is largely limited by the slow carrier; consequently, the high mobility carriers only increase the recombination current without aiding collection.","PeriodicalId":375453,"journal":{"name":"2012 15th International Workshop on Computational Electronics","volume":"124 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":"116012672","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.2012.6242862
B. Sen, M. Stroscio, M. Dutta
The piezoelectric effect in zincblende and wurtzite nanowires based on the full piezoelectric tensor following the continuum model has been studied analytically. Theoretical results present comparisons between piezoelectric potentials generated in wurtzite and zincblende nanowires which will serve as a guide for the proper design of future nanostructures in order to achieve maximum piezo-energy.
{"title":"Piezoelectric fields in quantum wires","authors":"B. Sen, M. Stroscio, M. Dutta","doi":"10.1109/IWCE.2012.6242862","DOIUrl":"https://doi.org/10.1109/IWCE.2012.6242862","url":null,"abstract":"The piezoelectric effect in zincblende and wurtzite nanowires based on the full piezoelectric tensor following the continuum model has been studied analytically. Theoretical results present comparisons between piezoelectric potentials generated in wurtzite and zincblende nanowires which will serve as a guide for the proper design of future nanostructures in order to achieve maximum piezo-energy.","PeriodicalId":375453,"journal":{"name":"2012 15th International Workshop on Computational Electronics","volume":"34 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":"128121480","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.2012.6242857
H. Ryu, Sunhee Lee, Y. H. Tan, B. Weber, S. Mahapatra, M. Simmons, L. Hollenberg, Gerhard Klimeck
Metallic property and Ohmic conduction in densely phosphorus δ-doping ultra-thin silicon nanowires (Si:P NWs) are studied. A 10-band sp3 d5 s* tight-binding approach is used to describe device electronic structures atomistically. Electrostatics at equilibrium are self-consistently calculated with our in-house 3-D parallel Schrödinger-Poisson solver that is coupled to the Local Density Approximation to consider the electron exchange-correlation in simulations. We not only confirm the NW channel is metallic by calculating the equilibrium bandstructure of a 1.5nm wide and 1/4 atomic monolayer doping [110] Si:P NW, but also provide a strong connection to experiment by calculating ohmic conduction properties of a few NW channels and showing a quantitatively good agreement to the measured data. This work can be highlighted as the first study of Si:P NWs with a full-band atomistic approach.
{"title":"Full-band study of ultra-thin Si:P nanowires","authors":"H. Ryu, Sunhee Lee, Y. H. Tan, B. Weber, S. Mahapatra, M. Simmons, L. Hollenberg, Gerhard Klimeck","doi":"10.1109/IWCE.2012.6242857","DOIUrl":"https://doi.org/10.1109/IWCE.2012.6242857","url":null,"abstract":"Metallic property and Ohmic conduction in densely phosphorus δ-doping ultra-thin silicon nanowires (Si:P NWs) are studied. A 10-band sp3 d5 s* tight-binding approach is used to describe device electronic structures atomistically. Electrostatics at equilibrium are self-consistently calculated with our in-house 3-D parallel Schrödinger-Poisson solver that is coupled to the Local Density Approximation to consider the electron exchange-correlation in simulations. We not only confirm the NW channel is metallic by calculating the equilibrium bandstructure of a 1.5nm wide and 1/4 atomic monolayer doping [110] Si:P NW, but also provide a strong connection to experiment by calculating ohmic conduction properties of a few NW channels and showing a quantitatively good agreement to the measured data. This work can be highlighted as the first study of Si:P NWs with a full-band atomistic approach.","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":"128820688","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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