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In this work, degradations of dynamic characteristics for silicon carbide (SiC) power metal-oxide-semiconductor field-effect transistors under repetitive avalanche shocks are investigated in details. With the help of Silvaco TCAD simulations, gate capacitance versus gate voltage (Cg–Vg) measurement, and three-terminal charge pumping test, the main damaged position is demonstrated to be the SiC/SiO2 interface along junction FET (JFET) region instead of the body diode where most of the avalanche current passes through. Dominant avalanche degradation mechanism is then confirmed to be the injection of holes into the gate oxide above the JFET region. Since the channel region and the main junction of body diode are not seriously damaged by the avalanche stress, static parameters all remain stable. Meanwhile, due to the injection of holes, the depletion layer beneath the JFET region gets thinner, resulting in the increase of gate-drain capacitance (Cgd) under low drain-source voltage (Vds) bias condition. It further takes responsibilities for the increments in input capacitance (Ciss), output capacitance (Coss), and reverse transfer capacitance (Crss). Moreover, it results in the extension of Miller plateau. Therefore, the increase of gate charge and delay of turn-off time after being stressed by repetitive avalanche shocks are monitored. Moreover, turn-on and turn-off dissipated energies after different unclamped-inductive-switching stress cycles are extracted. They are rarely influenced by the stress for the overlapping areas of voltage and current during switching procedures are relatively stable. [ABSTRACT FROM AUTHOR]

In this paper, an indirect decoupling method is established to simulate the physical process of an electromagnetic launch considering electromagnetic force, thermo-softening of metallic material, and melting interface layer effects. The dynamic responses of cambered surface rail and armature under electromagnetic and thermal loads are analyzed and a simulation method is provided for the engineering applications of electromagnetic launch technology. [ABSTRACT FROM PUBLISHER]

A method is presented to quantify the radiated power from a high-density connector. This method is based on network parameters and the principle of conservation of power. Unlike previous work, which assumed only radiated losses were present, the proposed method is able to characterize the radiated power in environments that contain material losses and when there are multiple signals at the printed circuit board/connector interface. The power losses are quantified through the definition of power loss constant matrices that can be used to find the power losses for arbitrary input excitations when the matrices are entirely known. The power loss constant matrices can be calculated through multiple single-port and two-port excitations for an N-port connector. The formulation of these excitations is dictated by the nonlinear properties of the power loss calculation. Simulations and measurements are presented that validate the proposed power loss calculation methodology. [ABSTRACT FROM AUTHOR]

This paper presents a numerical method to simulate the particle trajectory in the head–disk interface (HDI). The simulator solves the reduced Navier–Stokes equation with the second-slip boundary conditions to get the air velocity distribution, then solves the motion equations of particles and obtains the trajectories of the particles in the HDI using the binary Lagrange interpolation and the fourth-order Runge–Kutta method. The calculated trajectories of particles follow well with the air streamlines in the recessed regions. The particle density, diameter, and initial entering velocity have different effects on particle movement. Furthermore, particle velocity behaviors in the recessed regions are investigated for the first time. The particle is accelerated or decelerated by the action of the drag force and becomes close to the velocity of local air flow. Such effects are more obvious for small particles than large particles. The particle velocity becomes very small when it is close to the leading edge of the trailing pad. The numerical results also show that the particle goes up when it crosses the transition regions, and the particle moves upward more sharply with higher initial entrance height due to the larger vertical velocity of the local air flow. [ABSTRACT FROM AUTHOR]

We compare the simulations and measurements of gate leakage current in metal–insulator–semiconductor capacitors fabricated on standard AlGaN/GaN transistor layers. In the simulations, a fixed charge density at the interface between the Al2O3 layer and the GaN cap layer was assumed for simplicity. The fixed charge layer (which depends on bias and device history) was obtained from capacitance–voltage measurements. The calculated tunneling current due to field emission from localized states in the GaN cap layer agreed with the experimental results. No additional leakage mechanisms had to be invoked. [ABSTRACT FROM PUBLISHER]

In this paper, we introduce a modeling methodology for field bus-based embedded systems that allows dynamic evaluation of their signal integrity characteristics at the virtual prototyping step. Our methodology is based on the following criteria: 1) a signal integrity-aware I/O interface mixed model; 2) a physical model of transmission lines to estimate signal degradation caused by the bus lines; and 3) an ICEM model to estimate the impact of a chip's internal activity on its power voltage or its I/O. Through simulations and experimental validations, we show that our methodology allows functional validation of the design and can also evaluate some low-level effects such as the influence of an embedded software instruction on the voltage drops in the power rails. [ABSTRACT FROM PUBLISHER]

We present an analytical solution for coherent scattering of electromagnetic waves from a two-layer rough surface structure with uncorrelated random rough interfaces. The Kirchhoff approximation is used to predict the coherent (specular) component of the scattered wave from a layered rough surface that is assumed to have radii of curvature much larger than the wavelength to allow the application of the method. The roughness on both boundaries is assumed small such that the coherent component of the scattered wave is dominant. The derived solution includes all orders of the scattered wave and has a simple algebraic expression that can be readily computed. We validate the solution against a numerical method and present simulation results for various cases. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the dynamic response of two different bulk heterojunction organic photodetectors over a large illumination and frequency range. To our knowledge, there is no similar study that includes the nW/cm^2 regime. Photocurrent transient measurements reveal that the interlayer at the hole-extracting electrode is critical for the device performance under ultralow illumination. Furthermore, we observe a nonlinear cutoff frequency behavior over the illumination range, which we attribute to interface-related phenomena. We perform a detailed simulation study of the transient response for the measured samples. Making use of a drift diffusion model that also takes into account charge trapping and detrapping effects, both in bulk and at material interfaces, we are able to successfully reproduce the measured transients. Based on our simulations, we propose an explanation for this effect: it can be attributed to the interplay between the potential landscape seen by the charge carriers and to the presence of a large concentration of interface trap states, as well as of fixed interface charges. The importance of smart interface engineering as a key factor for device optimization is also highlighted. [ABSTRACT FROM AUTHOR]

This paper presents an improved algorithm for power hardware-in-loop (PHIL) simulation that takes the errors introduced by the interface equipment into account. Through modeling and analysis of a PHIL simulation circuit, which is composed of a voltage-source converter and a simple network, the impact of the bandwidth of the interface amplifier and equipment on the PHIL simulation is examined. Based on the analysis, an improved algorithm is proposed that uses additional interface filters (implemented in hardware and/or software) rather than the use of previously attempted compensation techniques. More stable and accurate results can be obtained by using the new algorithm. The validity of the proposed algorithm is verified through a software case study and hardware case studies. [ABSTRACT FROM AUTHOR]

A wide range zero-voltage switching (ZVS) active-clamped L-L type current-fed isolated dc–dc converter is proposed for fuel cells to utility interface application. The proposed converter maintains ZVS of all switches from full load down to very light load condition for wide input voltage variation. Detailed operation, analysis, design, simulation and experimental results for the proposed converter are presented. The auxiliary active clamping circuit absorbs the turn-off voltage spike and also assists in achieving ZVS of main switches. The ZVS of auxiliary switches and main switches is achieved by the energy stored in the boost inductors and series inductor (aided by parallel inductor), respectively. Rectifier diodes operate with zero-current switching. An experimental converter rated at 200 W has been designed, built and tested in the laboratory to verify the analysis, design and performance of the proposed converter for wide variations in input voltage and load. [ABSTRACT FROM AUTHOR]

The increased penetration of nonlinear loads and power-electronics-based distributed generation (DG) systems may introduce power quality issues to the distribution power system. However, if controlled and regulated properly, the DG–grid interfacing converters are able to improve the distribution system efficiency and power quality. This paper focuses on the distribution system harmonic control through the DG–grid interfacing converters. Two alternative DG systems, namely, current-controlled DG and voltage-controlled DG, are considered. While most of the previous works on harmonic compensation are based on the current-controlled method, a novel harmonic control scheme using a voltage-controlled method is developed in this paper. The voltage-controlled method is more flexible and has similar compensation performance compared to the conventional current-controlled method. In addition, by avoiding the implementation of a harmonic current tracking loop, the proposed voltage-based method can be seamlessly incorporated into a voltage-controlled DG unit, which is important to provide direct voltage and frequency support in a microgrid. Moreover, the possible harmonic circulating current among multiple DG systems is also investigated in this paper. Simulations and experimental results from a three-phase 5-kVA laboratory DG prototype are provided to validate the discussion. [ABSTRACT FROM AUTHOR]

Short-channel zinc oxide (ZnO) thin-film transistors (TFTs) are investigated in a wide range of temperatures and bias conditions. Scaling down the channel length, the TFT performance is seriously affected by contact resistances, which depend on gate voltage and temperature. To account for the contact resistances, the transistor is ideally split in three parts. The contact regions are modeled as two separate transistors with a fixed channel length and an exponential distribution of localized states, whereas the channel is treated as reported in Part I. The overall model reproduces the measured characteristics at different channel length, with a single set of physical and geometrical parameters. It can be readily implemented in a circuit simulator. Numerical simulations confirm the validity of the model approach and are used to evaluate the impact of nonidealities at the electrode/semiconductor interface. [ABSTRACT FROM PUBLISHER]

The interface between nano-scale films is of relevance in many critical applications. Specifically, recent technological advances in semiconductor industry that utilize silicon-on-insulator devices have given importance to the understanding of thermal transport across Si\-SiO2 interface. Estimates of interfacial (Kapitza) resistance to the thermal transport across Si\-SiO2 films do not appear to exist at the present time. In this paper, we develop and carryout reverse non-equilibrium molecular dynamics simulations by imposing known heat flux to determine the Kapitza resistance between Si\-SiO2 thin films. For the Si\-SiO2 interface, the average Kapitza resistance for a \sim8∼\rm\AA thick oxide layer system was 0.503 \times10^-9∼m^2K/W and for a \sim11.5∼\rm\AA thick oxide layer system was 0.518\,\times 10^-9∼m^2K/W. These values were of the same order of magnitude as the Kapitza resistance values determined from the acoustic mismatch model and the diffuse mismatch model for the Si\-SiO2 interface. [ABSTRACT FROM AUTHOR]

Rutherford Backscattering Spectrometry (RBS) using 6 MeV alpha particles and X-Ray Fluorescence (XRF) with a Pd-anode X-Ray generator were performed to characterize Au and Pt contacts deposited by electroless technique and thermal evaporation on differently treated surfaces of CdZnTe and CdTe crystals. The aim of this study is to understand and improve the structure of the material-electrode interface. The thickness, the stoichiometry and the concentration profiles of platinum, gold, cadmium, zinc, tellurium and oxygen present at the surface layers were determined. The distribution of Cd deficiency at the interface layers was profiled using simulations and showed complex profiles in the samples, which can greatly affect the electrical quality of the detectors. [ABSTRACT FROM AUTHOR]

An analytic and continuous direct-current model for cylindrical doped surrounding-gate metal–oxide–semiconductor field-effect transistors (SGMOSFETs) including interface-trap charges is presented. Based on the SGMOSFET model, which is valid from undoped to heavily doped channels, a general model for long-channel SGMOSFETs including interface-trap charges is derived. A comparison between the numerical simulations and analytic calculations showed that the proposed model is valid for all operating regions of SGMOSFETs including different interface-trap charges with several dimensions and doping densities. [ABSTRACT FROM PUBLISHER]

This paper proposes a new topology for bidirectional multiinput direct dc–ac converter for clean-power-generation system, therefore, at the input port, a boost converter is used to meet the requirement of many distributed generation systems, such as photovoltaic, and fuel cell systems. The boost converter can increase the dc input voltage. This point results in a turn ratio reduction of high-frequency isolating link transformer. Furthermore, the boost inductor reduces the input current ripple, therefore, the saturation of the transformer can be avoided for higher output currents. The count of used devices has been reduced in the proposed converter. As a result, the cost, size, and the volume of the converter can be reduced. The reduced conversion steps increase the efficiency of the converter. The converter is analyzed step by step to show the principles of the operation in providing energy management based on duty-cycle variations. The system capability in different operation conditions has been simulated, and the simulation results have been compared with measurement results. Dynamic analysis and control design of the bidirectional dc–ac converter is presented based on nonlinear control by input–output feedback linearization. [ABSTRACT FROM AUTHOR]

This paper presents a new neural-network method to describe the electromagnetic (EM) behavior at the interface between the substructures from an internally decomposed EM structure. A set of neural networks is used to represent the EM behavior of the substructure as seen from the interface. This allows EM coupling between substructures to be effectively represented. The method is developed in a finite-element environment. An EM transfer function matrix is formulated to produce training data, allowing neural networks to learn the spatial coupling between EM-field variables at various locations over the interface of the substructure. A new formulation is proposed where trained neural networks are integrated into the finite-element equation for efficient simulation of an overall EM structure. A technique is developed to allow the proposed model to be used with the mesh different from that in neural-network training. Examples show that the proposed method provides better accuracy than conventional neural-network approaches for modeling substructures from an internally decomposed EM problem. Using the proposed model also speeds up finite-element simulation. [ABSTRACT FROM AUTHOR]

A novel electric-circuit simulation model considering the contact and interface physics for electromagnetic railgun is suggested. The contact velocity skin-effect resistance and the contact resistance are considered. The pulsed-power supply is implemented with Simplorer V8, and the railgun is modeled by Matlab/Simulink. The data exchange is controlled by Simplorer V8. Nine experimental data have been used to validate the new model. Then, based on the validated model, a two-objective optimization pursuing both the highest velocity and the highest efficiency is carried out with the help of iSIGHT. [ABSTRACT FROM AUTHOR]

Analytical expressions for terminal charges of an independent-gate asymmetric double gate MOSFET (DGFET) are derived. The new charge model is Cinfin continuous, valid for all bias conditions and does not involve charge-sheet approximation. This is accomplished by developing the symmetric linearization method in the form that does not require identical boundary conditions at the two Si--SiO2 interfaces and allows for the volume inversion in the DGFET channel. Verification of the model is performed with both numerical computations and 2D TCAD simulations under a wide range of biasing conditions. The terminal charges expressions are similar to those in the PSP bulk MOSFET model and in the PSP-based common-gate symmetric DGFET model. The latter becomes a special case of the new model. [ABSTRACT FROM AUTHOR]

This paper deals with a theoretical study of the hot-spot onset (HSO) in cellular bipolar power transistors. This well-known phenomenon consists of a current crowding within few cells occurring for high power conditions, which significantly decreases the forward safe operating area (FSOA) of the device. The study was performed on a virtual sample by means of a fast, fully analytical electrothermal simulator operating in the steady state regime and under the condition of imposed input base current. The purpose was to study the dependence of the phenomenon on several thermal and geometrical factors and to test suitable countermeasures able to impinge this phenomenon at higher biases or to completely e!iminate it. The power threshold of HSO and its localization within the silicon die were observed as a function of the electrical bias conditions as for instance the collector voltage, the equivalent thermal resistance of the assembling structure underlying the silicon die, the value of the ballasting resistances purposely added in the emitter metal interconnections, and the thickness of the copper heat spreader placed on the die top just to the aim of making more uniform the temperature of the silicon surface. [ABSTRACT FROM AUTHOR]

A new solution to the problem of implementing extended-stencil finite-difference operators across material interfaces is presented in this paper for time-domain electromagnetic simulations. In essence, modified spatial approximations are applied within a transition layer that encloses the discontinuity, while preserving the stencil size of the scheme employed in the homogeneous areas. The necessary difference expressions are determined with the aid of a straightforward design procedure, which is based on the reliable modeling of exact solutions, following a one-dimensional formulation. The proposed approach, whose beneficial effects are exemplified via numerical simulations, is analyzed for the case of the (2,4) method. Yet, its concepts are global and easily adapted to any discretization algorithm. [ABSTRACT FROM AUTHOR]

This paper presents dynamic modeling and simulation of a grid connected variable speed wind turbine (VSWT) using PSCAD/EMTDC, a widely used power system transient analysis tool. The variable speed wind system with a direct-drive generator and power electronics interface is modeled for dynamic analysis. Component models and equations are addressed and their implementations into PSCAD/EMTDC are described. Controllable power inverter strategy is intended for capturing the maximum energy from varying wind speed and maintaining reactive power generation at a pre-determined level for constant power factor or voltage regulation. The component models and entire control scheme are constructed by user-defined function provided in the program. Simulation studies provide control performance and dynamic behavior of a gearless VSWT under varying wind speeds. In addition, the system responses to network fault conditions have been simulated. This modeling study can be employed to evaluate the control scheme, output performance and impacts of a VSWT on power grid at planning or designing stage. [ABSTRACT FROM AUTHOR]

We present a highly efficient optical field concentrator that is capable of confining optical field in nanometer-thin low-index media with very high optical confinement factor. The structure is made of multiple-layered low-index nanolayers embedded in high-index silicon waveguides. By creating multiple high-index-contrast interfaces, the normal field in the low-index nanolayer regions is significantly enhanced. It subsequently results in a very high optical confinement and power density in these regions. With the help of numerical simulation tools, the guiding and propagating characteristics of the new structure are studied and presented. The optimal structures have demonstrated confinement factors and normalized power densities in the range of 30%–60% and 20–160 μm-2 for the 5–20-nm thin low-index multiple nanolayers. [ABSTRACT FROM AUTHOR]