The Experts below are selected from a list of 324 Experts worldwide ranked by ideXlab platform
Sungmin Hong - One of the best experts on this subject based on the ideXlab platform.
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transient simulation of semiconductor devices using a deterministic boltzmann Equation Solver
IEEE Journal of the Electron Devices Society, 2018Co-Authors: Sungmin Hong, Jaehyung JangAbstract:In this paper, the transient simulation of semiconductor devices using a deterministic Boltzmann Equation Solver is presented. Transient simulation capability is implemented in a deterministic Boltzmann Equation Solver for the 3-D momentum space based on the spherical harmonics expansion. The numerical simulation results with implicit time marching methods demonstrate that the transient simulation using a deterministic Boltzmann Equation Solver can be performed. The impact of the quasi-static approximation for the current density, which is widely adopted in the momentum-based Equations, is tested for various devices such as homogeneous samples, an N+NN+ structure and an MOSFET.
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an efficient approach to include full band effects in deterministic boltzmann Equation Solver based on high order spherical harmonics expansion
IEEE Transactions on Electron Devices, 2011Co-Authors: Sungmin Hong, C JungemannAbstract:We present an efficient method to include full-band-structure effects for the case of a silicon conduction band in a deterministic Boltzmann Equation Solver based on the high-order spherical harmonics expansion method. This method employs the exact density of states and the group velocity obtained from band structure calculations, and it eliminates the modulus of the wave vector in the formulation such that an explicit invertible dispersion relation is not required. While the present method does not require additional central-processing-unit time and memory, compared with the analytic band model, the simulation results are significantly improved and in excellent agreement with those from the full-band Monte Carlo simulations and from an approach based on an invertible anisotropic band that matches several moments of the group velocity of the full band structure.
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a fully coupled scheme for a boltzmann poisson Equation Solver based on a spherical harmonics expansion
Journal of Computational Electronics, 2009Co-Authors: Sungmin Hong, C JungemannAbstract:The numerical properties of a deterministic Boltzmann Equation Solver based on a spherical harmonics expansion of the distribution function are analyzed and improved. A fully coupled discretization scheme of the Boltzmann and Poisson Equations is proposed, where stable Equations are obtained based on the H-transformation. It is explicitly shown that the resultant Jacobian matrix for the zeroth order component has property M for a first order expansion, which improves the stability even of higher order expansions. The detailed dependence of the free-streaming operator and the scattering operator on the electrostatic potential is exactly considered in the Newton-Raphson scheme. Therefore, convergence enhancement is achieved compared with previous Gummel-type approaches. This scheme is readily applicable to small-signal and noise analysis. As numerical examples, simulation results are shown for a silicon n + nn + structure including a magnetic field, an SOI NMOSFET and a SiGe HBT.
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A deterministic Boltzmann Equation Solver for two-dimensional semiconductor devices
2008 International Conference on Simulation of Semiconductor Processes and Devices, 2008Co-Authors: Sungmin Hong, Christoph Jungemann, Matthias BollhöferAbstract:We have developed a Boltzmann Equation Solver for two-dimensional (2D) semiconductor devices based on the spherical harmonics expansion and the maximum entropy dissipation scheme for stabilization. The large system of Equations is partitioned according to the order of the spherical harmonics and solved by a memory efficient blockwise Gauss-Seidel method. Results are presented for a 2D NPN Si bipolar junction transistor.
C Jungemann - One of the best experts on this subject based on the ideXlab platform.
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an efficient approach to include full band effects in deterministic boltzmann Equation Solver based on high order spherical harmonics expansion
IEEE Transactions on Electron Devices, 2011Co-Authors: Sungmin Hong, C JungemannAbstract:We present an efficient method to include full-band-structure effects for the case of a silicon conduction band in a deterministic Boltzmann Equation Solver based on the high-order spherical harmonics expansion method. This method employs the exact density of states and the group velocity obtained from band structure calculations, and it eliminates the modulus of the wave vector in the formulation such that an explicit invertible dispersion relation is not required. While the present method does not require additional central-processing-unit time and memory, compared with the analytic band model, the simulation results are significantly improved and in excellent agreement with those from the full-band Monte Carlo simulations and from an approach based on an invertible anisotropic band that matches several moments of the group velocity of the full band structure.
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a fully coupled scheme for a boltzmann poisson Equation Solver based on a spherical harmonics expansion
Journal of Computational Electronics, 2009Co-Authors: Sungmin Hong, C JungemannAbstract:The numerical properties of a deterministic Boltzmann Equation Solver based on a spherical harmonics expansion of the distribution function are analyzed and improved. A fully coupled discretization scheme of the Boltzmann and Poisson Equations is proposed, where stable Equations are obtained based on the H-transformation. It is explicitly shown that the resultant Jacobian matrix for the zeroth order component has property M for a first order expansion, which improves the stability even of higher order expansions. The detailed dependence of the free-streaming operator and the scattering operator on the electrostatic potential is exactly considered in the Newton-Raphson scheme. Therefore, convergence enhancement is achieved compared with previous Gummel-type approaches. This scheme is readily applicable to small-signal and noise analysis. As numerical examples, simulation results are shown for a silicon n + nn + structure including a magnetic field, an SOI NMOSFET and a SiGe HBT.
Juan Carlos Arceo - One of the best experts on this subject based on the ideXlab platform.
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the design and verification of a high performance low control overhead asynchronous differential Equation Solver
IEEE Transactions on Very Large Scale Integration Systems, 1998Co-Authors: Peter A Beerel, Vida Vakilotojar, A E Dooply, Juan Carlos ArceoAbstract:This paper describes the design and verification of a high-performance asynchronous differential Equation Solver benchmark circuit. The design has low-control-overhead which allows its average-case speed (tested at 22/spl deg/C and 3.3 V) to be 48% faster than any comparable synchronous design (designed to operate at 100/spl deg/C and 3 V for the slow process corner). The techniques to reduce completion sensing overhead and hide control overhead at the circuit, architectural, and protocol levels are discussed. In addition, symbolic model checking techniques are described that were used to gain higher confidence in the correctness of the timed distributed control.
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the design and verification of a high performance low control overhead asynchronous differential Equation Solver
International Symposium on Advanced Research in Asynchronous Circuits and Systems, 1997Co-Authors: Peter A Beerel, Vida Vakilotojar, A E Dooply, Juan Carlos ArceoAbstract:This paper describes the design and verification of a high-performance asynchronous differential Equation Solver. The design has low control overhead which allows the average-case delay to be 48% faster (tested at 22/spl deg/C and 3.3 V) than any comparable synchronous design (simulated at 100/spl deg/C and 3 V). The techniques to reduce completion sensing overhead and hide control overhead at the circuit, architectural, and protocol levels are discussed. In addition, symbolic model checking techniques are described that were used to gain higher confidence in the correctness of the timed distributed control.
Denis Zorin - One of the best experts on this subject based on the ideXlab platform.
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a high order 3d boundary integral Equation Solver for elliptic pdes in smooth domains
Journal of Computational Physics, 2006Co-Authors: Lexing Ying, George Biros, Denis ZorinAbstract:We present a high-order boundary integral Equation Solver for 3D elliptic boundary value problems on domains with smooth boundaries. We use Nystrom's method for discretization, and combine it with special quadrature rules for the singular kernels that appear in the boundary integrals. The overall asymptotic complexity of our method is O(N3/2), where N is the number of discretization points on the boundary of the domain, and corresponds to linear complexity in the number of uniformly sampled evaluation points. A kernel-independent fast summation algorithm is used to accelerate the evaluation of the discretized integral operators. We describe a high-order accurate method for evaluating the solution at arbitrary points inside the domain, including points close to the domain boundary. We demonstrate how our Solver, combined with a regular-grid spectral Solver, can be applied to problems with distributed sources. We present numerical results for the Stokes, Navier, and Poisson problems.
Firas Mourtada - One of the best experts on this subject based on the ideXlab platform.
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impact of heterogeneity based dose calculation using a deterministic grid based boltzmann Equation Solver for intracavitary brachytherapy
International Journal of Radiation Oncology Biology Physics, 2012Co-Authors: Justin Mikell, Ann H Klopp, Graciela Nogueras M Gonzalez, K Kisling, M Price, Paula A Berner, Patricia J Eifel, Firas MourtadaAbstract:Purpose To investigate the dosimetric impact of the heterogeneity dose calculation Acuros (Transpire Inc., Gig Harbor, WA), a grid-based Boltzmann Equation Solver (GBBS), for brachytherapy in a cohort of cervical cancer patients. Methods and Materials The impact of heterogeneities was retrospectively assessed in treatment plans for 26 patients who had previously received 192 Ir intracavitary brachytherapy for cervical cancer with computed tomography (CT)/magnetic resonance-compatible tandems and unshielded colpostats. The GBBS models sources, patient boundaries, applicators, and tissue heterogeneities. Multiple GBBS calculations were performed with and without solid model applicator, with and without overriding the patient contour to 1 g/cm 3 muscle, and with and without overriding contrast materials to muscle or 2.25 g/cm 3 bone. Impact of source and boundary modeling, applicator, tissue heterogeneities, and sensitivity of CT-to-material mapping of contrast were derived from the multiple calculations. American Association of Physicists in Medicine Task Group 43 (TG-43) guidelines and the GBBS were compared for the following clinical dosimetric parameters: Manchester points A and B, International Commission on Radiation Units and Measurements (ICRU) report 38 rectal and bladder points, three and nine o'clock, and D2cm3 to the bladder, rectum, and sigmoid. Results Points A and B, D 2 cm 3 bladder, ICRU bladder, and three and nine o'clock were within 5% of TG-43 for all GBBS calculations. The source and boundary and applicator account for most of the differences between the GBBS and TG-43 guidelines. The D 2cm3 rectum ( n = 3), D 2cm3 sigmoid ( n = 1), and ICRU rectum ( n = 6) had differences of >5% from TG-43 for the worst case incorrect mapping of contrast to bone. Clinical dosimetric parameters were within 5% of TG-43 when rectal and balloon contrast were mapped to bone and radiopaque packing was not overridden. Conclusions The GBBS has minimal impact on clinical parameters for this cohort of patients with unshielded applicators. The incorrect mapping of rectal and balloon contrast does not have a significant impact on clinical parameters. Rectal parameters may be sensitive to the mapping of radiopaque packing.
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dosimetric impact of an i192r brachytherapy source cable length modeled using a grid based boltzmann transport Equation Solver
Medical Physics, 2010Co-Authors: Justin Mikell, Firas MourtadaAbstract:Purpose: To evaluate the dose distributions of an I 192 r source (model VS2000) in homogeneous water geometry calculated using a deterministic grid-based Boltzmann transport Equation Solver (GBBS) in the commercial treatment planning system (TPS) (BRACHYVISION-ACUROS v8.8). Methods: Using percent dose differences ( % Δ D ) , the GBBS (BV-ACUROS) was compared to the (1) published TG-43 data, (2) MCNPXMonte Carlo(MC) simulations of the I 192 r source centered in a 15 cm radius water sphere, and (3) TG-43 output from the TPS using vendor supplied (BV-TG43-vendor) and user extended (BV-TG43-extended) 2D anisotropy functions F ( r , θ ) . BV-ACUROS assumes 1 mm of NiTi cable, while the TPS TG-43 algorithm uses data based on a 15 cm cable. MC models of various cable lengths were simulated. Results: The MC simulations resulted in > 20 % dose deviations along the cable for 1, 2, and 3 mm cable lengths relative to 15 cm. BV-ACUROS comparisons with BV-TG43-vendor and BV-TG43-extended yielded magnitude of differences, consistent with those seen in MC simulations. However, differences > 20 % extended further ( θ ≤ 10 ° ) when using the vendor supplied anisotropy function F ven ( r , θ ) . These differences were also seen in comparisons of F ( r , θ ) derived from the TPS output. Conclusions: The results suggest that % Δ D near the cable region is larger than previously estimated. The spatial distribution of the dose deviation is highly dependent on the reference TG-43 data used to compare to GBBS. The differences observed, while important to realize, should not have an impact on clinical dosimetry in homogeneous water.
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validation of a new grid based boltzmann Equation Solver for dose calculation in radiotherapy with photon beams
Physics in Medicine and Biology, 2010Co-Authors: Oleg N Vassiliev, Todd A Wareing, John M Mcghee, Gregory Failla, Mohammad Salehpour, Firas MourtadaAbstract:A new grid-based Boltzmann Equation Solver, Acuros™, was developed specifically for performing accurate and rapid radiotherapy dose calculations. In this study we benchmarked its performance against Monte Carlo for 6 and 18 MV photon beams in heterogeneous media. Acuros solves the coupled Boltzmann transport Equations for neutral and charged particles on a locally adaptive Cartesian grid. The Acuros Solver is an optimized rewrite of the general purpose Attila© software, and for comparable accuracy levels, it is roughly an order of magnitude faster than Attila. Comparisons were made between Monte Carlo (EGSnrc) and Acuros for 6 and 18 MV photon beams impinging on a slab phantom comprising tissue, bone and lung materials. To provide an accurate reference solution, Monte Carlo simulations were run to a tight statistical uncertainty (σ ≈ 0.1%) and fine resolution (1–2 mm). Acuros results were output on a 2 mm cubic voxel grid encompassing the entire phantom. Comparisons were also made for a breast treatment plan on an anthropomorphic phantom. For the slab phantom in regions where the dose exceeded 10% of the maximum dose, agreement between Acuros and Monte Carlo was within 2% of the local dose or 1 mm distance to agreement. For the breast case, agreement was within 2% of local dose or 2 mm distance to agreement in 99.9% of voxels where the dose exceeded 10% of the prescription dose. Elsewhere, in low dose regions, agreement for all cases was within 1% of the maximum dose. Since all Acuros calculations required less than 5 min on a dual-core two-processor workstation, it is efficient enough for routine clinical use. Additionally, since Acuros calculation times are only weakly dependent on the number of beams, Acuros may ideally be suited to arc therapies, where current clinical algorithms may incur long calculation times.
