Pub Date : 2009-05-27DOI: 10.1109/IWCE.2009.5091112
S. Steiger, R. Veprek, B. Witzigmann
Nonequilibrium Green's functions (NEGF) are employed to model carrier transport and luminescence in a single-quantum-well light-emitting diode (LED). The sound theoretical formalism allows for a consistent description of coherence loss as well as fundamental scattering mechanisms and reveals details about physical phenomena such as the quantum-confined Stark and Franz-Keldysh effects, tunneling and carrier capture. A comparison to semiclassical results is made and similarities as well as differences are highlighted.
{"title":"Electroluminescence from a Quantum-Well LED using NEGF","authors":"S. Steiger, R. Veprek, B. Witzigmann","doi":"10.1109/IWCE.2009.5091112","DOIUrl":"https://doi.org/10.1109/IWCE.2009.5091112","url":null,"abstract":"Nonequilibrium Green's functions (NEGF) are employed to model carrier transport and luminescence in a single-quantum-well light-emitting diode (LED). The sound theoretical formalism allows for a consistent description of coherence loss as well as fundamental scattering mechanisms and reveals details about physical phenomena such as the quantum-confined Stark and Franz-Keldysh effects, tunneling and carrier capture. A comparison to semiclassical results is made and similarities as well as differences are highlighted.","PeriodicalId":443119,"journal":{"name":"2009 13th International Workshop on Computational Electronics","volume":"18 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124154918","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 : 2009-05-27DOI: 10.1109/IWCE.2009.5091077
J. Shaw, T. Hou, H. Raza, E. Kan
We have shown the process variation effects from nanocrystal size, density, registry and gate length in 20-90 nm metal nanocrystal memory technology by 3D finite-element analysis. Conventional ID analysis in the gate stack will result in severe miscalculation of bit-error-rate due to neglecting the fringing fields and percolation path in the memory cell. We also present the statistical metrology on memory windows from nanocrystal placement control and the use of nanowire devices. We conclude that the self-assembled nanocrystals in the gate stack can fit the parametric yield required for 20 nm technology.
{"title":"3D Finite-Element Analysis of Metal Nanocrystal Memories Variations","authors":"J. Shaw, T. Hou, H. Raza, E. Kan","doi":"10.1109/IWCE.2009.5091077","DOIUrl":"https://doi.org/10.1109/IWCE.2009.5091077","url":null,"abstract":"We have shown the process variation effects from nanocrystal size, density, registry and gate length in 20-90 nm metal nanocrystal memory technology by 3D finite-element analysis. Conventional ID analysis in the gate stack will result in severe miscalculation of bit-error-rate due to neglecting the fringing fields and percolation path in the memory cell. We also present the statistical metrology on memory windows from nanocrystal placement control and the use of nanowire devices. We conclude that the self-assembled nanocrystals in the gate stack can fit the parametric yield required for 20 nm technology.","PeriodicalId":443119,"journal":{"name":"2009 13th International Workshop on Computational Electronics","volume":"173 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124251834","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 : 2009-05-27DOI: 10.1109/IWCE.2009.5091125
Tiao Lu, G. Du, Haiyan Jiang, Xiaoyan Liu, Pingwen Zhang
We present a self-consistent multi subband deter- ministic solver of the Boltzmann transport equation of the two dimensional (2D) electron gas. The Sch¨ odinger equation at each slice in the confinement direction and the two dimensional Poisson equation are self-consistently solved with the Boltzmann transport equation. The energy quantization and the scattering of the 2D electron gas are included. We apply this solver to an ultra-thin body double gate MOSFET and show the influence of the 2Dk scattering to the electron transport.
{"title":"Multi Subband Deterministic Simulation of an Ultra-thin Double Gate MOSFET with 2D Electron Gas","authors":"Tiao Lu, G. Du, Haiyan Jiang, Xiaoyan Liu, Pingwen Zhang","doi":"10.1109/IWCE.2009.5091125","DOIUrl":"https://doi.org/10.1109/IWCE.2009.5091125","url":null,"abstract":"We present a self-consistent multi subband deter- ministic solver of the Boltzmann transport equation of the two dimensional (2D) electron gas. The Sch¨ odinger equation at each slice in the confinement direction and the two dimensional Poisson equation are self-consistently solved with the Boltzmann transport equation. The energy quantization and the scattering of the 2D electron gas are included. We apply this solver to an ultra-thin body double gate MOSFET and show the influence of the 2Dk scattering to the electron transport.","PeriodicalId":443119,"journal":{"name":"2009 13th International Workshop on Computational Electronics","volume":"25 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129112565","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 : 2009-05-27DOI: 10.1109/IWCE.2009.5091090
T. Maiti, C. Maiti
Charge transport in organic semiconductors is investigated and a theoretical description of small polaron dc conductivity model is presented. The approach is based on Frohlich Hamiltonian. The model is implemented in a device simulator to analyze the electrical characteristics of pentacene-based Organic Thin Film Transistors (OTFT).
{"title":"Charge-based Mobility Modeling for Organic Semiconductors","authors":"T. Maiti, C. Maiti","doi":"10.1109/IWCE.2009.5091090","DOIUrl":"https://doi.org/10.1109/IWCE.2009.5091090","url":null,"abstract":"Charge transport in organic semiconductors is investigated and a theoretical description of small polaron dc conductivity model is presented. The approach is based on Frohlich Hamiltonian. The model is implemented in a device simulator to analyze the electrical characteristics of pentacene-based Organic Thin Film Transistors (OTFT).","PeriodicalId":443119,"journal":{"name":"2009 13th International Workshop on Computational Electronics","volume":"13 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114210817","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 : 2009-05-27DOI: 10.1109/IWCE.2009.5091110
M. Li, R. Zhang, Z. Zhang, W. Yan, B. Liu, D. Fu, C. Z. Zhao, Z. Xie, X. Xiu, Y. Zheng
Schrodinger equation and Poisson equation are solved self-consistently for Al 0.5 Ga 0.5 N/GaN heterojunctions grown along the c axis, then the distribution of electrons and the exact energy of all the bounded states confined in heterojunctions are gotten, and the electrons are found to take up the first two subbands. Considerable magnitude of Rashba spin splitting for the first subband at the Fermi level is obtained. The changes of Rashba spin splitting with barrier thickness, and doping concentration in the barrier are calculated. The results show that Rashba spin splitting in Al 0.5 Ga 0.5 N/GaN heterojunctions increase with doping concentration and the thickness of the barrier, and the internal electric field caused by piezoelectric polarization and the spontaneous polarization is crucial for considerable Rashba spin splitting in Al 0.5 Ga 0.5 N/GaN heterojunctions. Therefore, we can change barrier thickness and doping concentration to modulate internal electric field and then Rashba spin splitting in Alo 0.5 Ga 0.5 N/GaN heterojunctions.
对沿c轴生长的Al - 0.5 Ga - 0.5 N/GaN异质结的薛定谔方程和泊松方程进行了自洽求解，得到了异质结中电子的分布和所有束缚态的精确能量，发现电子占据了前两个子带。在费米能级上得到了第一子带的相当大的Rashba自旋分裂。计算了Rashba自旋分裂随势垒厚度和势垒中掺杂浓度的变化。结果表明，Al 0.5 Ga 0.5 N/GaN异质结中的Rashba自旋分裂随掺杂浓度和势垒厚度的增加而增加，压电极化和自发极化引起的内部电场是Al 0.5 Ga 0.5 N/GaN异质结中Rashba自旋分裂的关键。因此，我们可以通过改变势垒厚度和掺杂浓度来调制内部电场，从而在Alo 0.5 Ga 0.5 N/GaN异质结中实现Rashba自旋分裂。
{"title":"Effect of Doping Concentration and Barrier Thickness on Rashba Spin Splitting in Al0.5Ga0.5N/GaN Heterostructures","authors":"M. Li, R. Zhang, Z. Zhang, W. Yan, B. Liu, D. Fu, C. Z. Zhao, Z. Xie, X. Xiu, Y. Zheng","doi":"10.1109/IWCE.2009.5091110","DOIUrl":"https://doi.org/10.1109/IWCE.2009.5091110","url":null,"abstract":"Schrodinger equation and Poisson equation are solved self-consistently for Al 0.5 Ga 0.5 N/GaN heterojunctions grown along the c axis, then the distribution of electrons and the exact energy of all the bounded states confined in heterojunctions are gotten, and the electrons are found to take up the first two subbands. Considerable magnitude of Rashba spin splitting for the first subband at the Fermi level is obtained. The changes of Rashba spin splitting with barrier thickness, and doping concentration in the barrier are calculated. The results show that Rashba spin splitting in Al 0.5 Ga 0.5 N/GaN heterojunctions increase with doping concentration and the thickness of the barrier, and the internal electric field caused by piezoelectric polarization and the spontaneous polarization is crucial for considerable Rashba spin splitting in Al 0.5 Ga 0.5 N/GaN heterojunctions. Therefore, we can change barrier thickness and doping concentration to modulate internal electric field and then Rashba spin splitting in Alo 0.5 Ga 0.5 N/GaN heterojunctions.","PeriodicalId":443119,"journal":{"name":"2009 13th International Workshop on Computational Electronics","volume":"29 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116731854","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 : 2009-05-27DOI: 10.1109/IWCE.2009.5091084
Zhidong Chen, Jinyu Zhang, Zhiping Yu
The ac small-signal conductance of graphene nanoribbons (GNRs) was investigated using non-equilibrium Green's function. Simulation results of ac conductance of GNRs with and without the edge effect are presented. The edge effect and the influence of a slight change in width have great impacts on the ac conductance of GNRs. The ac conductance of GNRs presents oscillatory response with frequency. At low frequencies, a metallic GNR displays an inductive behavior, whereas a semi-conductive GNR displays a capacitive behavior.
{"title":"AC Small-Signal Response of Graphene Nanoribbons","authors":"Zhidong Chen, Jinyu Zhang, Zhiping Yu","doi":"10.1109/IWCE.2009.5091084","DOIUrl":"https://doi.org/10.1109/IWCE.2009.5091084","url":null,"abstract":"The ac small-signal conductance of graphene nanoribbons (GNRs) was investigated using non-equilibrium Green's function. Simulation results of ac conductance of GNRs with and without the edge effect are presented. The edge effect and the influence of a slight change in width have great impacts on the ac conductance of GNRs. The ac conductance of GNRs presents oscillatory response with frequency. At low frequencies, a metallic GNR displays an inductive behavior, whereas a semi-conductive GNR displays a capacitive behavior.","PeriodicalId":443119,"journal":{"name":"2009 13th International Workshop on Computational Electronics","volume":"32 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132789348","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 : 2009-05-27DOI: 10.1109/IWCE.2009.5091091
Yu He, Jinyu Zhang, Ming Zhang, Yan Wang, Zhiping Yu
We investigate both end-contact and side-contact structures between Al, Pd, Sc and carbon nanotube (CNT) in this paper. The different structures show the different chemical bonds and charge transfer at the metal-CNT contact interfaces. A novel method based on dipole effect is proposed to calculate the Schottky barrier height (SBH). Different SBHs for the contacts are due to different electro-negativity of metal atoms as well as the chemical bonds.
{"title":"Chemical Bonding and Schottky Barrier for Metal-Carbon Nanotube Contacts","authors":"Yu He, Jinyu Zhang, Ming Zhang, Yan Wang, Zhiping Yu","doi":"10.1109/IWCE.2009.5091091","DOIUrl":"https://doi.org/10.1109/IWCE.2009.5091091","url":null,"abstract":"We investigate both end-contact and side-contact structures between Al, Pd, Sc and carbon nanotube (CNT) in this paper. The different structures show the different chemical bonds and charge transfer at the metal-CNT contact interfaces. A novel method based on dipole effect is proposed to calculate the Schottky barrier height (SBH). Different SBHs for the contacts are due to different electro-negativity of metal atoms as well as the chemical bonds.","PeriodicalId":443119,"journal":{"name":"2009 13th International Workshop on Computational Electronics","volume":"106 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131753332","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 : 2009-05-27DOI: 10.1109/IWCE.2009.5091108
I. M. Tienda-Luna, F. Ruiz, A. Godoy, F. Gámiz
A variety of techniques can be employed to increase the drive current in CMOS transistors. In this paper, we study the effects of using different wafer orientations and strain methods in surrounding gate transistors. Specifically, we focus on Quantum Electron Density and mobility. A significant modification of both magnitudes is to be expected, due to the changes caused in the effective mass tensor and in the conduction band edge position.
{"title":"Effect of Arbitrary Orientation and Strain on Surrounding Gate Transistors","authors":"I. M. Tienda-Luna, F. Ruiz, A. Godoy, F. Gámiz","doi":"10.1109/IWCE.2009.5091108","DOIUrl":"https://doi.org/10.1109/IWCE.2009.5091108","url":null,"abstract":"A variety of techniques can be employed to increase the drive current in CMOS transistors. In this paper, we study the effects of using different wafer orientations and strain methods in surrounding gate transistors. Specifically, we focus on Quantum Electron Density and mobility. A significant modification of both magnitudes is to be expected, due to the changes caused in the effective mass tensor and in the conduction band edge position.","PeriodicalId":443119,"journal":{"name":"2009 13th International Workshop on Computational Electronics","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116778711","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 : 2009-05-27DOI: 10.1109/IWCE.2009.5091098
K. Lam, G. Liang
In our ab initio study on the device performance of nitrogen-doped monolayer zigzag GNR (ZGNR) FETs, an increase in ZGNR width from 0.92 nm to 1.78 nm degrades the I max |I min ratio due to the decrease in the energy bandgap (Eg) which causes the I min to increase. It is also observed that the presence of vacancy at the edges of the channel ribbon can also open up an Eg in ZGNRs as nitrogen dopants, and the performance of such device depends greatly on the vacancy concentration. In addition, simulation was carried out on the nitrogen-doped bilayer ZGNR FET and comparing to the monolayer ZGNR FET, the bilayer device provides a larger current while the I max |I min is lowered.
在我们对氮掺杂单层之字形GNR (ZGNR) fet器件性能的从头算研究中，ZGNR宽度从0.92 nm增加到1.78 nm，由于能带隙(Eg)的减小导致I min增加，导致I max bb0 I min比降低。在氮掺杂zgnr中，沟道带边缘空位的存在也会打开一个Eg，而空位浓度在很大程度上决定了器件的性能。此外，对氮掺杂双层ZGNR FET进行了仿真，与单层ZGNR FET相比，双层器件提供了更大的电流，而imax | imin降低。
{"title":"Computational Study on the Performance Comparison of Monolayer and Bilayer Zigzag Graphene Nanoribbon FETs","authors":"K. Lam, G. Liang","doi":"10.1109/IWCE.2009.5091098","DOIUrl":"https://doi.org/10.1109/IWCE.2009.5091098","url":null,"abstract":"In our ab initio study on the device performance of nitrogen-doped monolayer zigzag GNR (ZGNR) FETs, an increase in ZGNR width from 0.92 nm to 1.78 nm degrades the I max |I min ratio due to the decrease in the energy bandgap (Eg) which causes the I min to increase. It is also observed that the presence of vacancy at the edges of the channel ribbon can also open up an Eg in ZGNRs as nitrogen dopants, and the performance of such device depends greatly on the vacancy concentration. In addition, simulation was carried out on the nitrogen-doped bilayer ZGNR FET and comparing to the monolayer ZGNR FET, the bilayer device provides a larger current while the I max |I min is lowered.","PeriodicalId":443119,"journal":{"name":"2009 13th International Workshop on Computational Electronics","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117072230","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 : 2009-05-27DOI: 10.1109/IWCE.2009.5091137
Z. Akšamija, Mohamed Mohamed, Umberto Ravaioli
This works treats electronic transport in SWNTs in the Boltzmann Transport equation (BTE) formalism. The BTE is solved self-consistently with the Poisson equation and iterated in time using an upwinding finite-difference scheme until a steady-state is reached. Phonon scattering is included through a relaxation time based on experimental values reported in the literature. The problem is parallelized by dividing the real space into strips, where each strip is assigned to one processing element to minimize communication overhead. The implementation was tested on a many-processor cluster and shows good speed-up over the serial code. This demonstrates that the code is capable of excellent scaling to large supercomputing machines for large-scale parallel simulation of nanotubes, as well as other similar 1-dimensional materials like nanoribbons and nanowires.
{"title":"Parallel Implementation of Boltzmann Transport Simulation of Carbon Nanotubes","authors":"Z. Akšamija, Mohamed Mohamed, Umberto Ravaioli","doi":"10.1109/IWCE.2009.5091137","DOIUrl":"https://doi.org/10.1109/IWCE.2009.5091137","url":null,"abstract":"This works treats electronic transport in SWNTs in the Boltzmann Transport equation (BTE) formalism. The BTE is solved self-consistently with the Poisson equation and iterated in time using an upwinding finite-difference scheme until a steady-state is reached. Phonon scattering is included through a relaxation time based on experimental values reported in the literature. The problem is parallelized by dividing the real space into strips, where each strip is assigned to one processing element to minimize communication overhead. The implementation was tested on a many-processor cluster and shows good speed-up over the serial code. This demonstrates that the code is capable of excellent scaling to large supercomputing machines for large-scale parallel simulation of nanotubes, as well as other similar 1-dimensional materials like nanoribbons and nanowires.","PeriodicalId":443119,"journal":{"name":"2009 13th International Workshop on Computational Electronics","volume":"38 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115508165","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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