This manual describes the use of the Xyce Parallel Electronic Simulator. Xyce has been designed as a SPICE-compatible, high-performance analog circuit simulator, and has been written to support the simulation needs of the Sandia National Laboratories electrical designers. This development has focused on improving capability over the current state-of-the-art in the following areas: (1) Capability to solve extremely large circuit problems by supporting large-scale parallel computing platforms (up to thousands of processors). This includes support for most popular parallel and serial computers. (2) A differential-algebraic-equation (DAE) formulation, which better isolates the device model package from solver algorithms. This allows one to develop new types of analysis without requiring the implementation of analysis-specific device models. (3) Device models that are specifically tailored to meet Sandia’s needs, including some radiation-aware devices (for Sandia users only). (4) Object-oriented code design and implementation using modern coding practices. Xyce is a parallel code in the most general sense of the phrase — a message passing parallel implementation — which allows it to run efficiently a wide range of computing platforms. These include serial, shared-memory and distributed-memory parallel platforms. Attention has been paid to the specific nature of circuit-simulation problems to ensure that optimal parallel efficiency is achieved as the number of processors grows.
The Xyce™ Parallel Electronic Simulator has been written to support the simulation needs of Sandia National Laboratories’ electrical designers. Xyce™ is a SPICE-compatible simulator with the ability to solve extremely large circuit problems on large-scale parallel computing platforms, but also includes support for most popular parallel and serial computers.
This manual gives usage information for the Charon semiconductor device simulator. Charon was developed to meet the modeling needs of Sandia National Laboratories and to improve on the capabilities of the commercial TCAD simulators; in particular, the additional capabilities are running very large simulations on parallel computers and modeling displacement damage and other radiation effects in significant detail. The parallel capabilities are based around the MPI interface which allows the code to be ported to a large number of parallel systems, including linux clusters and proprietary “big iron” systems found at the national laboratories and in large industrial settings.
This manual gives usage information for the Charon semiconductor device simulator. Charon was developed to meet the modeling needs of Sandia National Laboratories and to improve on the capabilities of the commercial TCAD simulators; in particular, the additional capabilities are running very large simulations on parallel computers and modeling displacement damage and other radiation effects in significant detail. The parallel capabilities are based around the MPI interface which allows the code to be ported to a large number of parallel systems, including linux clusters and proprietary "big iron" systems found at the national laboratories and in large industrial settings.
We present a comprehensive physics investigation of electrothermal effects in III-V heterojunction bipolar transistors (HBTs) via extensive Technology Computer Aided Design (TCAD) simulation and modeling. We show for the first time that the negative differential resistances of the common-emitter output responses in InGaP/GaAs HBTs are caused not only by the well-known carrier mobility reduction, but more importantly also by the increased base-To-emitter hole back injection, as the device temperature increases from self-heating. Both self-heating and impact ionization can cause fly-backs in the output responses under constant base-emitter voltages. We find that the fly-back behavior is due to competing processes of carrier recombination and self-heating or impact ionization induced carrier generation. These findings will allow us to understand and potentially improve the safe operating areas and circuit compact models of InGaP/GaAs HBTs.
We present a comprehensive physics investigation of electrothermal effects in III-V heterojunction bipolar transistors (HBTs) via extensive Technology Computer Aided Design (TCAD) simulation and modeling. We show for the first time that the negative differential resistances of the common-emitter output responses in InGaP/GaAs HBTs are caused not only by the well-known carrier mobility reduction, but more importantly also by the increased base-To-emitter hole back injection, as the device temperature increases from self-heating. Both self-heating and impact ionization can cause fly-backs in the output responses under constant base-emitter voltages. We find that the fly-back behavior is due to competing processes of carrier recombination and self-heating or impact ionization induced carrier generation. These findings will allow us to understand and potentially improve the safe operating areas and circuit compact models of InGaP/GaAs HBTs.
We present an analytic band-to-trap tunneling model developed using the open boundary scattering approach. The new model explicitly includes the effect of heterojunction band offset, in addition to the well known electric field effect. Its analytic form enables straightforward implementation into TCAD device and circuit simulators. The model is capable of simulating both electric field and band offset enhanced carrier recombination due to the band-to-trap tunneling in the depletion region near a heterojunction. Simulation results of an InGaP/GaAs heterojunction bipolar transistor reveal that the proposed model predicts significantly increased base currents, because the hole-to-trap tunneling from the base to the emitter is greatly enhanced by the emitter base heterojunction band offset. The results compare favorably with experimental observations. The developed method can be applied to all one dimensional potentials which can be approximated to a good degree such that the approximated potentials lead to piecewise analytic wave functions with open boundary conditions.
We present an analytic band-to-trap tunneling model developed using the open boundary scattering approach. The new model explicitly includes the effect of heterojunction band offset, in addition to the well known electric field effect. Its analytic form enables straightforward implementation into TCAD device and circuit simulators. The model is capable of simulating both electric field and band offset enhanced carrier recombination due to the band-to-trap tunneling in the depletion region near a heterojunction. Simulation results of an InGaP/GaAs heterojunction bipolar transistor reveal that the proposed model predicts significantly increased base currents, because the hole-to-trap tunneling from the base to the emitter is greatly enhanced by the emitter base heterojunction band offset. The results compare favorably with experimental observations. The developed method can be applied to all one dimensional potentials which can be approximated to a good degree such that the approximated potentials lead to piecewise analytic wave functions with open boundary conditions.
The solution of the governing steady transport equations for momentum, heat and mass transfer in fluids undergoing non-equilibrium chemical reactions can be extremely challenging. The difficulties arise from both the complexity of the nonlinear solution behavior as well as the nonlinear, coupled, non-symmetric nature of the system of algebraic equations that results from spatial discretization of the PDEs. In this paper, we briefly review progress on developing a stabilized finite element (FE) capability for numerical solution of these challenging problems. The discussion considers the stabilized FE formulation for the low Mach number Navier-Stokes equations with heat and mass transport with non-equilibrium chemical reactions, and the solution methods necessary for detailed analysis of these complex systems. The solution algorithms include robust nonlinear and linear solution schemes, parameter continuation methods, and linear stability analysis techniques. Our discussion considers computational efficiency, scalability, and some implementation issues of the solution methods. Computational results are presented for a CFD benchmark problem as well as for a number of large-scale, 2D and 3D, engineering transport/reaction applications.
The solution of the governing steady transport equations for momentum, heat and mass transfer in fluids undergoing non-equilibrium chemical reactions can be extremely challenging. The difficulties arise from both the complexity of the nonlinear solution behavior as well as the nonlinear, coupled, non-symmetric nature of the system of algebraic equations that results from spatial discretization of the PDEs. In this paper, we briefly review progress on developing a stabilized finite element ( FE) capability for numerical solution of these challenging problems. The discussion considers the stabilized FE formulation for the low Mach number Navier-Stokes equations with heat and mass transport with non-equilibrium chemical reactions, and the solution methods necessary for detailed analysis of these complex systems. The solution algorithms include robust nonlinear and linear solution schemes, parameter continuation methods, and linear stability analysis techniques. Our discussion considers computational efficiency, scalability, and some implementation issues of the solution methods. Computational results are presented for a CFD benchmark problem as well as for a number of large-scale, 2D and 3D, engineering transport/reaction applications.
Multifidelity modeling, in which one component of a system is modeled at a significantly different level of fidelity than another, has several potential advantages. For example, a higher-fidelity component model can be evaluated in the context of a lower-fidelity full system model that provides more realistic boundary conditions and yet can be executed quickly enough for rapid design changes or design optimization. Developing such multifidelity models presents challenges in several areas, including coupling models with differing spatial dimensionalities. In this report we describe a multifidelity algorithm for thermal radiation problems in which a three-dimensional, finite-element model of a system component is embedded in a system of zero-dimensional (lumped-parameter) components. We tested the algorithm on a prototype system with three problems: heating to a constant temperature, cooling to a constant temperature, and a simulated fire environment. The prototype system consisted of an aeroshell enclosing three components, one of which was represented by a three-dimensional finite-element model. We tested two versions of the algorithm; one used the surface-average temperature of the three dimensional component to couple it to the system model, and the other used the volume-average temperature. Using the surface-average temperature provided somewhat better temperature predictions than using the volume-average temperature. Our results illustrate the difficulty in specifying consistency for multifidelity models. In particular, we show that two models may be consistent for one application but not for another. While the temperatures predicted by the multifidelity model were not as accurate as those predicted by a full three-dimensional model, our results show that a multifidelity system model can potentially execute much faster than a full three-dimensional finite-element model for thermal radiation problems with sufficient accuracy for some applications, while still predicting internal temperatures for the higher fidelity component. These results indicate that optimization studies with mixed-fidelity models are feasible when they may not be feasible with three-dimensional system models, if the concomitant loss in accuracy is within acceptable bounds.
This report describes research and development of methods to couple vastly different subsystems and physical models and to encapsulate these methods in a Java{trademark}-based framework. The work described here focused on developing a capability to enable design engineers and safety analysts to perform multifidelity, multiphysics analyses more simply. In particular this report describes a multifidelity algorithm for thermal radiative heat transfer and illustrates its performance. Additionally, it describes a module-based computer software architecture that facilitates multifidelity, multiphysics simulations. The architecture is currently being used to develop an environment for modeling the effects of radiation on electronic circuits in support of the FY 2003 Hostile Environments Milestone for the Accelerated Strategic Computing Initiative.