A three‐dimensional Monte Carlo model for the simulation of nanoelectronic devices

We present a three‐dimensional (3D) semi‐classical ensemble Monte Carlo model newly developed to simulate a variety of nanoelectronic devices. The characteristics of the 3D model are compared with the widely used two‐dimensional (2D) models. The advantages of our model, in terms of accuracy in modelling the physics behind the operation of nanodevices, are presented by applying it to T‐branch junctions based on InGaAs/InAlAs heterostructures. Simulation of a T‐branch junction with a Schottky gate terminal is presented, using both 2D and 3D models, demonstrating the necessity of using 3D simulation models to study the physics of complex‐geometry nanostructures. Copyright © 2009 John Wiley & Sons, Ltd.     

A note on the thermal modelling of power semiconductor devices using the network analogue

The aim of this note is to point out that the boundary condition for the network modelling of thermal problems may have been incorrectly used in some previous studies. It is shown that the accuracy of the network analogue or the equivalent finite‐difference method is on the par with the finite‐element method for very fast transient thermal simulations. Copyright © 2002 John Wiley & Sons, Ltd.     

Device‐partition method using equivalent circuit model in two‐dimensional device simulation

In order to accomplish two‐dimensional device simulation with a large number of nodes, in this paper we propose the device‐partition method (DPM) to resolve the problem that the memory size of the simulation environment is insufficient. The idea of DPM is that the device can be divided into several parts and a matrix solver only solves one part at a time. DPM uses the iteration method to simulate the device. By continuous iteration, an accurate solution can be obtained. Hence, we use DPM to demonstrate the simulations of the MOSFET and the CMOS inverter. The simulation results of DPM and the coupled method (CM) are nearly approximate and correspond with the theory. Hence, DPM is a suitable method to develop a powerful simulation environment. Copyright © 2005 John Wiley & Sons, Ltd.     

Fast alternating direction implicit method for efficient transient thermal simulation of integrated circuits

This paper presents fast alternating direction implicit (FADI) method for efficient transient thermal simulation of integrated circuits. The FADI method is formulated from Peaceman–Rachford's ADI and Douglas–Gunn's ADI methods. The update procedure of the proposed method has basic implicit form that features derivative‐free right‐hand side and hence, better efficiency and conciseness. Subsequently, through the basic implicit form of FADI method, the relationship between classical Peaceman–Rachford's and Douglas–Gunn's ADI methods can be clarified and elucidated in detail. A unified boundary condition that can cater to common kinds of boundary conditions in thermal simulation is also introduced. To further accelerate FADI method, the graphics processing unit is also utilized through Compute Unified Device Architecture implementation. It is shown that high efficiency gain can be achieved using the proposed FADI method through large time step size and data parallelism, while maintaining stability and good accuracy. As numerical illustration, an integrated circuit structure with microchannel cooling is demonstrated. Numerical results further ascertain the cooling effect of the microchannels. Copyright © 2015 John Wiley & Sons, Ltd.     

Use of WKB approximation for analytical boundary conditions in numerical solution of Schrödinger equation: application to semiconductor–high‐k dielectric interfaces

Numerical methods used to solve 1D Schrödinger's equation in quantum structures, such as Numerov's integration of wavefunction or the shooting method iterative solution of energy levels, require knowledge of two‐point boundary conditions at interfaces. This is especially true when the interfaces are not symmetrical or where exponential decay of wavefunction at asymptotically large distances does not hold. A closed‐form expression for boundary conditions, which is not sensitive to intermediate solutions at interfaces, can minimize possible divergence during iterations and relax simulation grid size and simulation time. In this work, the Wentzel‐Kramers‐Brillouin (WKB) approximation within potential barriers is proposed to analytically calculate the boundary conditions for abrupt interfaces, such as dielectric–semiconductor interface. An analytical expression for the slope at the interface is derived, and the errors are estimated with respect to numerical methods. An application is shown for self‐consistent solution of coupled Poisson–Schrödinger's equations at multi‐layer HfO₂‐SiO₂ dielectric gate stack corresponding to International Technology Roadmap for Semiconductors‐projected 10 nm bulk single‐gate Complementary Metal‐Oxide‐Semiconductor (CMOS) technology node, where wavefunction penetration into the dielectric is of critical importance. Application to dual gate structures with 5 nm fin width and high‐k dielectric with 0.5 nm equivalent oxide thickness is also shown. A quantum mechanical simulator ‘hksim’ based on this principle is posted for public domain usage. Copyright © 2015 John Wiley & Sons, Ltd.     

Long‐term reliability evaluation of power semiconductor devices used in power station rectifiers and substation rectifiers

In power stations and substations of electric power companies, power semiconductor devices such as diodes and thyristors have been used in control power supplies and emergency power supplies since the 1970s. Such equipment is designed on the assumption that power semiconductor devices are semipermanent, since their service life is much longer than that of capacitors and resistors. Therefore, it is hard to find studies that have systematically examined the long‐term reliability of semiconductor devices. Such studies are very important from the viewpoint of ensuring reliability and improving the renewal period by proper equipment maintenance. This paper discusses the long‐term reliability of power semiconductor devices used in power station rectifiers and substation rectifiers. © 2001 Scripta Technica, Electr Eng Jpn, 136(3): 67–75, 2001     

Global modeling of nonlinear circuits using the finite‐difference Laguerre time‐domain/alternative direction implicit finite‐difference time‐domain method with stability investigation

This paper describes a new unconditionally stable numerical method for the full‐wave physical modeling of semiconductor devices by a combination of the finite‐difference Laguerre time‐domain (FDLTD) and alternative direction implicit finite‐difference time‐domain (ADI‐FDTD) approaches. The unconditionally stable method by using FDLTD scheme for the electromagnetic model and semi‐implicit ADI‐FDTD approach for the active model leads to a significant decrease in the full‐wave simulation time. Numerical simulations of an example transistor and a power amplifier show the efficiency of presented method for the full‐wave simulation of mm‐wave active circuits. Copyright © 2012 John Wiley & Sons, Ltd.     

Transient analysis of coupled non‐uniform transmission line using finite element method

This paper presents a finite element time domain model for a numerical solution of a coupled non‐uniform transmission line problem. On the basis of the finite element method, a novel numerical procedure for the solution of a system of the non‐uniform multi‐conductor transmission line equations in the time domain is presented. The results obtained by the proposed method have been compared with the solution obtained using the finite difference time domain method, and an excellent correlation has been demonstrated. Copyright © 2014 John Wiley & Sons, Ltd.     

Investigation of the dark electrical characteristics of the lateral metal–semiconductor–metal photodetectors using two‐dimensional numerical simulation

A detailed investigation of the dark electrical characteristics of the lateral metal–semiconductor–metal (MSM) structures is carried out using a two‐dimensional numerical simulation based on the drift‐diffusion model. The model includes image force barrier lowering and current‐dependent recombination velocities at the Schottky contacts. The simulation was used to examine the details of the depletion region, the electric field distributions, and the current path in the active region of the planar structure. The obtained results were shown to be very helpful to understand and to explain various behaviours seen in the characteristics of the metal–semiconductor–metal (MSM) structures. The dark I‐V characteristics of the structure were also calculated and compared with published experimental data. The results reveal the importance of the image force lowering on the characteristics and the hole injection at the forward contact beyond the flat band voltage. Copyright © 2010 John Wiley & Sons, Ltd.     

Stochastic H∞ control problem with state‐dependent noise for weakly coupled large‐scale systems

In this paper, stochastic H_∞ state feedback control with state‐dependent noise for weakly coupled large‐scale systems is discussed. After establishing the asymptotic structure of the stochastic algebraic Riccati equation (SARE), a new iterative algorithm that combines the Newton's method with the fixed‐point algorithm is derived for the first time. As a result, both the quadratic convergence and the reduced‐order computation in the same dimension of the subsystems are attained. Copyright © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Monte Carlo simulation for stochastic calculus of far‐field radiation from open‐ended waveguide arrays

In this paper, Monte Carlo (MC) simulation has been applied for the analysis and stochastic calculus of far‐field radiation from the small, large, and infinite open‐ended waveguide arrays. Elements of the arrays are excited by the fundamental TE₁₀ mode and with equal amplitude and linear phase. The simulated results from MC are compared closely with the finite element method (FEM). Numerical analysis based on FEM is performed using Ansoft High Frequency Structural Simulator to calculate the far‐field radiation characteristics of the arrays. The accuracy and the effectiveness of the aforesaid method, which is based on Monte Carlo integration technique, are also demonstrated in uniformly and nonuniformly spaced waveguide arrays for pattern synthesis or achieving side lobe level reduction. The arrays with arbitrary shapes are simply evaluated by MC method in equal spacing array. It is found that by applying MC simulation, the open‐ended waveguide arrays have the ability to produce the desired radiation pattern and could satisfy requirements for many applications. Copyright © 2016 John Wiley & Sons, Ltd.     

Investigation of numerical time‐integrations of Maxwell's equations using the staggered grid spatial discretization

The Yee‐method is a simple and elegant way of solving the time‐dependent Maxwell's equations. On the other hand, this method has some inherent drawbacks too. The main one is that its stability requires a very strict upper bound for the possible time‐steps. This is why, during the last decade, the main goal was to construct such methods that are unconditionally stable. This means that the time‐step can be chosen based only on accuracy instead of stability considerations. In this paper we give a uniform treatment of methods that use the same spatial staggered grid approximation as the classical Yee‐method. Three other numerical methods are discussed: the Namiki–Zheng–Chen–Zhang alternating direction implicit method (NZCZ), the Kole–Figge‐de Raedt method (KFR) and a Krylov‐space method. All methods are discussed with non‐homogeneous material parameters. We show how the existing finite difference numerical methods are based on the approximation of a matrix exponential. With this formulation we prove the unconditional stability of the NZCZ method without any computer algebraic tool. Moreover, we accelerate the Krylov‐space method with a skew‐symmetric formulation of the semi‐discretized equations. Our main goal is to compare the methods from the point of view of the computational speed. This question is investigated in ID numerical tests. Copyright © 2005 John Wiley & Sons, Ltd.     

Fast analysis of finite and curved frequency‐selective surfaces using the VSIE with MLFMA

The hybrid volume‐surface integral equation approach is proposed to analyze the transmission and reflection characteristics of finite and curved frequency‐selective surfaces structures. The surface current and electric flux density are expanded by surface RWG and volume SWG basis functions, respectively. The multilevel fast multipole algorithm is applied to reduce the computational complexity. Simulated results are given to demonstrate the accuracy and efficiency of the proposed method. Copyright © 2010 John Wiley & Sons, Ltd.     

On the development of efficient FDTD‐PML formulations for general dispersive media

A novel implementation of the perfectly matched layer (PML) absorbing boundary condition (ABC) to terminate the finite‐difference time‐domain (FDTD) algorithm for general dispersive and negative index materials is presented. The proposed formulation also adopts the complex frequency‐shifted (CFS) approach, involves simple FDTD expressions and avoids complex arithmetic. Several FDTD‐PML simulations with different parameters are conducted for the termination of various dispersive media validating the stability, accuracy and effectiveness of the schemes and indicating the advantage of the CFS‐PML. Copyright © 2008 John Wiley & Sons, Ltd.     

A generalized CAD model for the full‐wave modeling of Coplanar striplines discontinuities

In this work, the coplanar stripline (CPS) and its discontinuities: open‐end, short‐end, gaps and resonator have been modeled. New integral equations for the electrical field components are formulated, in the spectral domain, using an exact dyadic Green's function, applied to the CPS structure. The use of this form of Green's function allows the consideration of the effects of the dielectric losses, the surface wave excitation and the space wave radiation on the propagation characteristics of the CPS and its discontinuities. The resulting integral equation has been solved using the two‐dimensional Galerkin's technique. The resolution of the resulting matrix equation gives the scattering parameters of the studied structures. The obtained results are commented and compared with those of other approaches and measurements. Copyright © 2011 John Wiley & Sons, Ltd.     

Electromagnetic analysis coupled with motion for high‐speed circuit breakers of eddy current repulsion using the tableau approach

Electromagnetic field analysis coupled with motion using the tableau approach has been applied to high‐speed circuit breakers of eddy current repulsion mechanisms. This breaker has an opening time of 1 ms and break time less than 1 cycle (20 ms). The driving part of the breaker is composed of electromagnetic repulsion mechanisms and disk springs with nonlinear characteristics. The mechanisms are composed of two fixed coils and one repulsion plate. A numeric experiment has been applied to investigate the dynamic behavior of the electromagnetic repulsion mechanism using the equivalent circuit method. Calculation results were in good agreement with both measurement results and calculation results by FEM on an experimental model. In addition, repulsive forces depending on material conductivities have been researched. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 152(4): 8–16, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20149     

Application of the recursion‐transform method in calculating the equivalent resistance of two‐dimensional finite resistor network

Looking for a handy and exact calculation for the equivalent resistance of an M × N resistor network is important but difficult, even for the rectangular resistor network. In this paper, we calculate the equivalent resistance of an M × N rectangular resistor network by means of the recursion‐transform method, where the idea of multiple external current sources based on the typical mesh current is used, and find a new formula of equivalent resistance which is different from the result of the other paper. In our scheme, recalculations are not required to obtain the equivalent resistance between different terminals. We further investigate how the order of resistor network and the ratio between two unit resistances affect the equivalent resistance. We find that the equivalent resistance between arbitrary terminals tends to a constant as the order and ratio increase when M is given. Copyright © 2016 John Wiley & Sons, Ltd.