Pub Date : 2014-06-03DOI: 10.1109/IWCE.2014.6865824
D. Osintsev, V. Sverdlov, N. Neophytou, S. Selberherr
Spintronics attracts much attention because of the potential to build novel spin-based devices which are superior to nowadays charge-based microelectronic devices. Silicon, the main element of microelectronics, is promising for spin-driven applications. We investigate the surface roughness and electron-phonon limited spin relaxation in silicon films taking into account the coupling between the relevant valleys through the Γ-point. We demonstrate that applying uniaxial stress along the [110] direction considerably suppresses the spin relaxation.
{"title":"Valley splitting and spin lifetime enhancement in strained thin silicon films","authors":"D. Osintsev, V. Sverdlov, N. Neophytou, S. Selberherr","doi":"10.1109/IWCE.2014.6865824","DOIUrl":"https://doi.org/10.1109/IWCE.2014.6865824","url":null,"abstract":"Spintronics attracts much attention because of the potential to build novel spin-based devices which are superior to nowadays charge-based microelectronic devices. Silicon, the main element of microelectronics, is promising for spin-driven applications. We investigate the surface roughness and electron-phonon limited spin relaxation in silicon films taking into account the coupling between the relevant valleys through the Γ-point. We demonstrate that applying uniaxial stress along the [110] direction considerably suppresses the spin relaxation.","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":"115498843","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.2014.6865856
M. Choi, N. Zhang, M. Dutta, M. Stroscio, Carlos O. Aspetti, R. Agarwal
Coherent interface phonon generation by surface plasmon in silver-SiO2-silicon system is analyzed, based on the impulsive stimulated scattering theory model. The surface plasmon is first analyzed, and applied to semiclassical stimulated Raman scattering theory. Our calculatation shows that the photon-induced surface plasmons store about 20-30% of the total incoming energy, and it is considered in the analysis. Phonon potential of the generated phonons is also calculated.
{"title":"Plasmon excitation of coherent interface phonons in Si-SiO2 systems","authors":"M. Choi, N. Zhang, M. Dutta, M. Stroscio, Carlos O. Aspetti, R. Agarwal","doi":"10.1109/IWCE.2014.6865856","DOIUrl":"https://doi.org/10.1109/IWCE.2014.6865856","url":null,"abstract":"Coherent interface phonon generation by surface plasmon in silver-SiO2-silicon system is analyzed, based on the impulsive stimulated scattering theory model. The surface plasmon is first analyzed, and applied to semiclassical stimulated Raman scattering theory. Our calculatation shows that the photon-induced surface plasmons store about 20-30% of the total incoming energy, and it is considered in the analysis. Phonon potential of the generated phonons is also calculated.","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":"128444335","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.2014.6865810
Lidija Filipović, O. Baumgartner, Z. Stanojević, H. Kosina
This work focuses on studying band-to-band tunneling in 3D devices, while considering variations in material properties (mass, doping), applied bias, or geometry. A simulation study of cylindrical nanowires, tapered structures and doping concentration variation demonstrates the importance of 3D effects in band-to-band tunneling current computation.
{"title":"Band-to-band tunneling in 3D devices","authors":"Lidija Filipović, O. Baumgartner, Z. Stanojević, H. Kosina","doi":"10.1109/IWCE.2014.6865810","DOIUrl":"https://doi.org/10.1109/IWCE.2014.6865810","url":null,"abstract":"This work focuses on studying band-to-band tunneling in 3D devices, while considering variations in material properties (mass, doping), applied bias, or geometry. A simulation study of cylindrical nanowires, tapered structures and doping concentration variation demonstrates the importance of 3D effects in band-to-band tunneling current computation.","PeriodicalId":168149,"journal":{"name":"2014 International Workshop on Computational Electronics (IWCE)","volume":"571 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":"132138033","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.2014.6865858
S. Karishy, J. Ajaka, C. Palermo, L. Varani
We use a hydrodynamic model self-consistently coupled to a 1D Poisson solver to simulate the excitation by optical beating as well as by electrical perturbation of plasma waves in n+nn+ InGaAs diodes at room temperature. We calculate the electric field response and the velocity response of the carriers in the middle of the diode regions. Our results show clearly the presence of three-dimensional plasma resonances in the terahertz frequency domain for the two region types (n and n+). The investigation is completed by calculating the local differential mobility.
{"title":"Vertical diodes response to optical and electrical THz excitations","authors":"S. Karishy, J. Ajaka, C. Palermo, L. Varani","doi":"10.1109/IWCE.2014.6865858","DOIUrl":"https://doi.org/10.1109/IWCE.2014.6865858","url":null,"abstract":"We use a hydrodynamic model self-consistently coupled to a 1D Poisson solver to simulate the excitation by optical beating as well as by electrical perturbation of plasma waves in n+nn+ InGaAs diodes at room temperature. We calculate the electric field response and the velocity response of the carriers in the middle of the diode regions. Our results show clearly the presence of three-dimensional plasma resonances in the terahertz frequency domain for the two region types (n and n+). The investigation is completed by calculating the local differential mobility.","PeriodicalId":168149,"journal":{"name":"2014 International Workshop on Computational Electronics (IWCE)","volume":"13 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":"130269950","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.2014.6865872
D. P. Adorno, P. Alaimo, N. Pizzolato, B. Spagnolo
The results of a study concerning the intrinsic noise in low-doped n-type InP crystals operating under static, periodic or fluctuating electric fields are shown. To simulate the dynamics of electrons in the bulk, we employ a Monte Carlo approach, by taking into account the main details of band structure, scattering processes, as well as heating effects. The noise features are investigated by computing the velocity fluctuations correlation function, its spectral density and the total noise power, for different values of amplitude and frequency of the driving field. We show how the noise spectra are affected by the electric field frequency and compare their peculiarities with those exhibited in the static field case. Preliminary findings obtained in InP crystals driven by an electric field fluctuating for the superimposition of a correlated noise source are discussed and compared with those previously obtained in GaAs bulks. Our results confirm that the diffusion noise in low-doped semiconductors can be reduced by the addition of a fluctuating component to the driving electric field and that this effect critically depends on the characteristic times of the external noise.
{"title":"Noise features in InP crystals operating under static, periodic or fluctuating electric fields","authors":"D. P. Adorno, P. Alaimo, N. Pizzolato, B. Spagnolo","doi":"10.1109/IWCE.2014.6865872","DOIUrl":"https://doi.org/10.1109/IWCE.2014.6865872","url":null,"abstract":"The results of a study concerning the intrinsic noise in low-doped n-type InP crystals operating under static, periodic or fluctuating electric fields are shown. To simulate the dynamics of electrons in the bulk, we employ a Monte Carlo approach, by taking into account the main details of band structure, scattering processes, as well as heating effects. The noise features are investigated by computing the velocity fluctuations correlation function, its spectral density and the total noise power, for different values of amplitude and frequency of the driving field. We show how the noise spectra are affected by the electric field frequency and compare their peculiarities with those exhibited in the static field case. Preliminary findings obtained in InP crystals driven by an electric field fluctuating for the superimposition of a correlated noise source are discussed and compared with those previously obtained in GaAs bulks. Our results confirm that the diffusion noise in low-doped semiconductors can be reduced by the addition of a fluctuating component to the driving electric field and that this effect critically depends on the characteristic times of the external noise.","PeriodicalId":168149,"journal":{"name":"2014 International Workshop on Computational Electronics (IWCE)","volume":"53 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":"128876061","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.2014.6865828
E. Chen, Yen-Tien Tung, Z. Xiao, T. Shen, Jeff Wu, Carlos H. Díaz
The ab initio work quantitatively explains the physical mechanism of threshold voltage shifts in n-type and p-type metal-oxide-semiconductor field-effect transistors with HfO2/Al2O3 gate stack. In the study, the θ phase alumina has been chosen for better lattice matching of the (100) HfO2 and (100) Si substrate. Using dipole correction method, the dominant dipole moment responsible for the threshold voltage shift has been identified at the interface of HfO2/Al2O3. Our HfO2/Al2O3 atomic model shows the dipole moment decreases almost linearly as the alumina thickness decreases from four monolayers (13 Å) to one monolayer (3 Å). On account of the effects of capacitance and the dipole moment, our ab initio calculation quantitatively explains the trend and sensitivity of experimental threshold voltage shifts on n- and p-MOSFET's.
{"title":"Ab initio study of dipole-induced threshold voltage shift in HfO2/Al2O3/(100)Si","authors":"E. Chen, Yen-Tien Tung, Z. Xiao, T. Shen, Jeff Wu, Carlos H. Díaz","doi":"10.1109/IWCE.2014.6865828","DOIUrl":"https://doi.org/10.1109/IWCE.2014.6865828","url":null,"abstract":"The ab initio work quantitatively explains the physical mechanism of threshold voltage shifts in n-type and p-type metal-oxide-semiconductor field-effect transistors with HfO<sub>2</sub>/Al<sub>2</sub>O<sub>3</sub> gate stack. In the study, the θ phase alumina has been chosen for better lattice matching of the (100) HfO<sub>2</sub> and (100) Si substrate. Using dipole correction method, the dominant dipole moment responsible for the threshold voltage shift has been identified at the interface of HfO<sub>2</sub>/Al<sub>2</sub>O<sub>3</sub>. Our HfO<sub>2</sub>/Al<sub>2</sub>O<sub>3</sub> atomic model shows the dipole moment decreases almost linearly as the alumina thickness decreases from four monolayers (13 Å) to one monolayer (3 Å). On account of the effects of capacitance and the dipole moment, our ab initio calculation quantitatively explains the trend and sensitivity of experimental threshold voltage shifts on n- and p-MOSFET's.","PeriodicalId":168149,"journal":{"name":"2014 International Workshop on Computational Electronics (IWCE)","volume":"23 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":"126906878","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.2014.6865857
Yi Lan, N. Zhang, J. Shi, M. Dutta, M. Stroscio
Herein, we consider examine the possibility of photodetectors with reduced signal-to-noise based on a three quantum well structure with one single well and one double well. This structure facilitates photon detection through the following sequence of events: photon absorption, phonon emission, and then photon absorb of a photon having the same wavelength as the first one. Even though this design two photons a phonon-assisted transition, it is demonstrated that greatly enhance signal-to-noise is obtained.
{"title":"Enhanced signal-to-noise in photodetectors due to interface phonon-assisted transitions","authors":"Yi Lan, N. Zhang, J. Shi, M. Dutta, M. Stroscio","doi":"10.1109/IWCE.2014.6865857","DOIUrl":"https://doi.org/10.1109/IWCE.2014.6865857","url":null,"abstract":"Herein, we consider examine the possibility of photodetectors with reduced signal-to-noise based on a three quantum well structure with one single well and one double well. This structure facilitates photon detection through the following sequence of events: photon absorption, phonon emission, and then photon absorb of a photon having the same wavelength as the first one. Even though this design two photons a phonon-assisted transition, it is demonstrated that greatly enhance signal-to-noise is obtained.","PeriodicalId":168149,"journal":{"name":"2014 International Workshop on Computational Electronics (IWCE)","volume":"98 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":"115155869","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.2014.6865808
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.2014.6865847
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}
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