Pub Date : 2014-06-03DOI: 10.1109/IWCE.2014.6865867
S. Yaro, X. Oriols
In time dependent (classical or quantum) particle-based simulators, one needs an algorithm to determine when (and with which properties) electrons are injected from the reservoir into the simulation box. In this work we develop an electron injection model for 2D materials with linear-dispersion materials. The injected model is based on satisfying the required phase-space density of electrons. In particular, we discuss the differences between a garphene-based electron injection model and older models developed for parabolic-dispersion materials. The linear dispersion of graphene implies unexpected restrictions when developing the injection model.
{"title":"Electron injection model for graphene","authors":"S. Yaro, X. Oriols","doi":"10.1109/IWCE.2014.6865867","DOIUrl":"https://doi.org/10.1109/IWCE.2014.6865867","url":null,"abstract":"In time dependent (classical or quantum) particle-based simulators, one needs an algorithm to determine when (and with which properties) electrons are injected from the reservoir into the simulation box. In this work we develop an electron injection model for 2D materials with linear-dispersion materials. The injected model is based on satisfying the required phase-space density of electrons. In particular, we discuss the differences between a garphene-based electron injection model and older models developed for parabolic-dispersion materials. The linear dispersion of graphene implies unexpected restrictions when developing the injection model.","PeriodicalId":168149,"journal":{"name":"2014 International Workshop on Computational Electronics (IWCE)","volume":"50 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":"133642336","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.2014.6865849
F. Buscemi, M. Rudan, E. Piccinini, R. Brunetti
The so-called Numerov process provides a three-point interpolation with an ~η5 accuracy in grid's size η, much better than the standard finite-difference scheme that keeps the ~η2 terms. Such a substantial improvement is achieved with a negligible increase in computational cost. As the method is applicable to second-order differential equations in one dimension, it is an ideal tool for solving, e.g., the Poisson and Schrödinger equations in ballistic electron devices, where the longitudinal (that is, along the channel) problem is typically separated from the lateral one and solved over a uniform grid. Despite its advantage, the Numerov process has found limited applications, due to the difficulty of keeping the same precision in the boundary conditions. A method to work out the boundary conditions consistently with the rest of the scheme is presented, and applications are shown.
{"title":"A 5th-order method for 1D-device solution","authors":"F. Buscemi, M. Rudan, E. Piccinini, R. Brunetti","doi":"10.1109/IWCE.2014.6865849","DOIUrl":"https://doi.org/10.1109/IWCE.2014.6865849","url":null,"abstract":"The so-called Numerov process provides a three-point interpolation with an ~η5 accuracy in grid's size η, much better than the standard finite-difference scheme that keeps the ~η2 terms. Such a substantial improvement is achieved with a negligible increase in computational cost. As the method is applicable to second-order differential equations in one dimension, it is an ideal tool for solving, e.g., the Poisson and Schrödinger equations in ballistic electron devices, where the longitudinal (that is, along the channel) problem is typically separated from the lateral one and solved over a uniform grid. Despite its advantage, the Numerov process has found limited applications, due to the difficulty of keeping the same precision in the boundary conditions. A method to work out the boundary conditions consistently with the rest of the scheme is presented, and applications are shown.","PeriodicalId":168149,"journal":{"name":"2014 International Workshop on Computational Electronics (IWCE)","volume":"117 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":"117259342","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.2014.6865881
S. Malakooti, Y. S. Joe, E. Hedin
A defective double stranded poly(dG)-poly(dC) DNA molecule under axial mechanical strain is analyzed using a tight-binding computational model which allows calculation of the transmission and current characteristics of the system as a function of electron energy. Results show the existence of highly sensitive electron transmission behavior with respect to the on-site energy perturbations.
{"title":"The effects of molecular elongation on defective DNA electronics","authors":"S. Malakooti, Y. S. Joe, E. Hedin","doi":"10.1109/IWCE.2014.6865881","DOIUrl":"https://doi.org/10.1109/IWCE.2014.6865881","url":null,"abstract":"A defective double stranded poly(dG)-poly(dC) DNA molecule under axial mechanical strain is analyzed using a tight-binding computational model which allows calculation of the transmission and current characteristics of the system as a function of electron energy. Results show the existence of highly sensitive electron transmission behavior with respect to the on-site energy perturbations.","PeriodicalId":168149,"journal":{"name":"2014 International Workshop on Computational Electronics (IWCE)","volume":"369 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":"122345063","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.2014.6865847
R. Rosati, F. Rossi
Starting from a density-matrix treatment of carrier-phonon interaction based on a recent reformulation of the Markov limit, we provide a detailed investigation of phonon-induced quantum diffusion in semiconductor nanostructures. In particular, as for the case of carrier-carrier relaxation in photoex-cited semiconductors, our analysis shows the failure of simplified dephasing models in describing phonon-induced scattering non-locality, pointing out that such limitation is particularly severe for the case of quasielastic dissipation processes.
{"title":"Phonon-induced quantum diffusion in semiconductors","authors":"R. Rosati, F. Rossi","doi":"10.1109/IWCE.2014.6865847","DOIUrl":"https://doi.org/10.1109/IWCE.2014.6865847","url":null,"abstract":"Starting from a density-matrix treatment of carrier-phonon interaction based on a recent reformulation of the Markov limit, we provide a detailed investigation of phonon-induced quantum diffusion in semiconductor nanostructures. In particular, as for the case of carrier-carrier relaxation in photoex-cited semiconductors, our analysis shows the failure of simplified dephasing models in describing phonon-induced scattering non-locality, pointing out that such limitation is particularly severe for the case of quasielastic dissipation processes.","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":"128721891","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.2014.6865808
B. Gaury, J. Weston, C. Groth, X. Waintal
With the technical progress of radio-frequency setups, high frequency quantum transport experiments have moved from theory to the lab. So far the standard theoretical approach used to treat such problems numerically - known as Keldysh or NEGF (Non Equilibrium Green's Functions) formalism - has not been very successful mainly because of a prohibitive computational cost. We propose a reformulation of the non-equilibrium Green's function technique in terms of the electronic wave functions of the system in an energy-time representation. The numerical algorithm we obtain scales now linearly with the simulated time and the volume of the system, and makes simulation of systems with 105-106 atoms/sites feasible. We illustrate our method with the propagation and spreading of a charge pulse in the quantum Hall regime. We identify a classical and a quantum regime for the spreading, depending on the number of particles contained in the pulse. This numerical experiment is the condensed matter analogue to the spreading of a Gaussian wavepacket discussed in quantum mechanics textbooks.
{"title":"Classical and quantum spreading of a charge pulse","authors":"B. Gaury, J. Weston, C. Groth, X. Waintal","doi":"10.1109/IWCE.2014.6865808","DOIUrl":"https://doi.org/10.1109/IWCE.2014.6865808","url":null,"abstract":"With the technical progress of radio-frequency setups, high frequency quantum transport experiments have moved from theory to the lab. So far the standard theoretical approach used to treat such problems numerically - known as Keldysh or NEGF (Non Equilibrium Green's Functions) formalism - has not been very successful mainly because of a prohibitive computational cost. We propose a reformulation of the non-equilibrium Green's function technique in terms of the electronic wave functions of the system in an energy-time representation. The numerical algorithm we obtain scales now linearly with the simulated time and the volume of the system, and makes simulation of systems with 105-106 atoms/sites feasible. We illustrate our method with the propagation and spreading of a charge pulse in the quantum Hall regime. We identify a classical and a quantum regime for the spreading, depending on the number of particles contained in the pulse. This numerical experiment is the condensed matter analogue to the spreading of a Gaussian wavepacket discussed in quantum mechanics textbooks.","PeriodicalId":168149,"journal":{"name":"2014 International Workshop on Computational Electronics (IWCE)","volume":"40 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":"122848917","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.2014.6865842
E. Hedin, Y. S. Joe
Multiple, serially-connected nanoscale rings are analyzed using a tight-binding computational algorithm which allows calculation of the transmission and current characteristics of the system as a function of energy and external magnetic flux. Results show the role of bilateral symmetry in the system response to imposed flux, which can shift the system from metallic to semiconducting.
{"title":"Serially-connected Aharonov-Bohm rings with embedded quantum dots","authors":"E. Hedin, Y. S. Joe","doi":"10.1109/IWCE.2014.6865842","DOIUrl":"https://doi.org/10.1109/IWCE.2014.6865842","url":null,"abstract":"Multiple, serially-connected nanoscale rings are analyzed using a tight-binding computational algorithm which allows calculation of the transmission and current characteristics of the system as a function of energy and external magnetic flux. Results show the role of bilateral symmetry in the system response to imposed flux, which can shift the system from metallic to semiconducting.","PeriodicalId":168149,"journal":{"name":"2014 International Workshop on Computational Electronics (IWCE)","volume":"142 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":"124541961","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.2014.6865845
P. Chang, Xiaoyan Liu, L. Zeng, K. Wei, G. Du
Hole mobility in ultra-thin body (UTB) InSb-OI devices is calculated by a microscopic approach. An adaptive grid algorithm is employed to discretize 2-D k space. The accurate valence band structures are obtained via solving the 6-band k·p Schrödinger and Poisson equations self-consistently. Hole mobility is computed using the Kubo-Greenwood formalism accounting for nonpolar acoustic and optical phonons, polar optical phonons, and surface roughness scattering mechanisms.
{"title":"An adaptive grid algorithm for self-consistent k·p Schrodinger and Poisson equations in UTB InSb-based pMOSFETs","authors":"P. Chang, Xiaoyan Liu, L. Zeng, K. Wei, G. Du","doi":"10.1109/IWCE.2014.6865845","DOIUrl":"https://doi.org/10.1109/IWCE.2014.6865845","url":null,"abstract":"Hole mobility in ultra-thin body (UTB) InSb-OI devices is calculated by a microscopic approach. An adaptive grid algorithm is employed to discretize 2-D k space. The accurate valence band structures are obtained via solving the 6-band k·p Schrödinger and Poisson equations self-consistently. Hole mobility is computed using the Kubo-Greenwood formalism accounting for nonpolar acoustic and optical phonons, polar optical phonons, and surface roughness scattering mechanisms.","PeriodicalId":168149,"journal":{"name":"2014 International Workshop on Computational Electronics (IWCE)","volume":"58 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":"125710798","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.2014.6865860
A. Garcia-Rivera, E. Comesaña, A. García-Loureiro, R. Valin, A. Martinez
In this paper different roughness profiles of transparent conductive oxide (TCO) have been simulated to calibrate a thin-film hydrogenated amorphous silicon double-junction tandem solar cell (a-Si:H/a-Si:H) against the experimental data. The TCO texture was modelled using a periodic triangular profile. The width of the period was kept constant and the height is changed according to the simulated angle α. The optimum roughness for the a-Si:H/a-Si:H solar cell was obtained for α = 26°. For this angle, the current density-voltage (J-V) characteristic has a good agreement with the J-V experimental data. The optimum value of α is close to the characteristics of an Asahi U-type texture used in the manufacturing process for the TCO and it generates the maximum electron density in the intrinsic layers.
{"title":"Influence of textured interfaces in the performance of a-Si:H double-junction solar cell","authors":"A. Garcia-Rivera, E. Comesaña, A. García-Loureiro, R. Valin, A. Martinez","doi":"10.1109/IWCE.2014.6865860","DOIUrl":"https://doi.org/10.1109/IWCE.2014.6865860","url":null,"abstract":"In this paper different roughness profiles of transparent conductive oxide (TCO) have been simulated to calibrate a thin-film hydrogenated amorphous silicon double-junction tandem solar cell (a-Si:H/a-Si:H) against the experimental data. The TCO texture was modelled using a periodic triangular profile. The width of the period was kept constant and the height is changed according to the simulated angle α. The optimum roughness for the a-Si:H/a-Si:H solar cell was obtained for α = 26°. For this angle, the current density-voltage (J-V) characteristic has a good agreement with the J-V experimental data. The optimum value of α is close to the characteristics of an Asahi U-type texture used in the manufacturing process for the TCO and it generates the maximum electron density in the intrinsic layers.","PeriodicalId":168149,"journal":{"name":"2014 International Workshop on Computational Electronics (IWCE)","volume":"31 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":"127254179","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.2014.6865853
M. L. Van de Put, M. Thewissen, W. Magnus, B. Sorée, J. Sellier
The Wigner-Liouville (WL) equation is well suited to describe electronic transport in semiconductor devices. In the effective mass approximation the one dimensional WL equation reads ∂/∂t f(x, p, t) + p/m ∂/∂x f(x, p, t)-1/h2 ∫ dp' W(x, p-p')f(x, p', t) = 0; (1) with the Wigner kernel given by W(x, p) = -i/2π ∫ dx' exp (-i px'/h) [V (x + x'/2)-V (x-x'/2)].(2) The Wigner kernel introduces a non-local interaction with the potential V(x), in accordance with quantum theory. Unfortunately, even for this simple interaction the mathematical form includes a highly oscillatory component (exp [-i p·x/h]) which impedes stable numerical implementation based on finite differences or finite elements.
{"title":"Spectral force approach to solve the time-dependent Wigner-Liouville equation","authors":"M. L. Van de Put, M. Thewissen, W. Magnus, B. Sorée, J. Sellier","doi":"10.1109/IWCE.2014.6865853","DOIUrl":"https://doi.org/10.1109/IWCE.2014.6865853","url":null,"abstract":"The Wigner-Liouville (WL) equation is well suited to describe electronic transport in semiconductor devices. In the effective mass approximation the one dimensional WL equation reads ∂/∂t f(x, p, t) + p/m ∂/∂x f(x, p, t)-1/h2 ∫ dp' W(x, p-p')f(x, p', t) = 0; (1) with the Wigner kernel given by W(x, p) = -i/2π ∫ dx' exp (-i px'/h) [V (x + x'/2)-V (x-x'/2)].(2) The Wigner kernel introduces a non-local interaction with the potential V(x), in accordance with quantum theory. Unfortunately, even for this simple interaction the mathematical form includes a highly oscillatory component (exp [-i p·x/h]) which impedes stable numerical implementation based on finite differences or finite elements.","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":"130524156","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.2014.6865864
J. Larroque, J. Saint-Martin, P. Dollfus
We show that with a Full-Band dispersion, the specific heat is closer to the experimental value than with an isotropic quadratic dispersion. So we use a Full-Band dispersion in the transport algorithm. A Monte Carlo algorithm has been developed to simulate phonon transport in silicon nanowire. It has been successfully used to simulate the thermal conductivity.
{"title":"Phonon transport in silicon nanowires using a Full-Band Monte Carlo approach","authors":"J. Larroque, J. Saint-Martin, P. Dollfus","doi":"10.1109/IWCE.2014.6865864","DOIUrl":"https://doi.org/10.1109/IWCE.2014.6865864","url":null,"abstract":"We show that with a Full-Band dispersion, the specific heat is closer to the experimental value than with an isotropic quadratic dispersion. So we use a Full-Band dispersion in the transport algorithm. A Monte Carlo algorithm has been developed to simulate phonon transport in silicon nanowire. It has been successfully used to simulate the thermal conductivity.","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":"129873871","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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