Compact Simulation Model Research Articles

Thermal dependence of the current in TiN/Ti/HfO2/W memristors at different intermediate conduction states

The dependence of the current in TiN/Ti/HfO2/W devices on the temperature is investigated in the range from 78 K to 340 K. Resistive switching cycles at 78 K are conducted to explore the thermal dependence in filament configurations with different intermediate resistance states. The less conductive states show an increase of the current as the temperature rises, while the fully formed filament displays a metallic-like behavior. A comprehensive model, based on the Stanford Model including a series resistance, is proposed and successfully validated by experimental data. The interplay between the ohmic and non-linear components in the model for different filament states is analyzed, emphasizing the dominance of the non-linear component (and its corresponding thermal dependence) in partially formed filaments and the prevalence of the ohmic component in the fully formed filament, which shows a decreasing current as the temperature rises. A complete compact model for simulation of circuits including the thermal dependence of these devices is developed.

A complete compact model for simulation of organic electronic systems

Organic Electronics provides multiple technological advantages such as low cost, flexibility, solution processability and waste reduction through the use of new materials and alternative fabrication techniques in the microelectronic world. The use of additive and printed fabrication processes allows the development of instantly fabricated, fully additive, low temperature processing together with lightweight, bendable, scalable and sustainable systems. Different models have been presented in the field but none of them with an industrial implementation. Complete simulation models are very useful for circuit production and commercialization since the organic electronics market is expected to grow in the near future and the need for industrial solutions for designers will increase. For this reason and for the first time, we present a compact model of DC and AC behaviour combined with different ambient conditions and parameter variability for full organic electronic system simulations.

High-fidelity circuit simulation of AQFP circuits through compact models extracted from layout

Adiabatic Quantum Flux Parametron (AQFP) superconductor logic circuits rely on magnetic coupling between the gate and clock and control lines to function. Circuit designers start by designing a circuit netlist, selecting parameters to fit design objectives, optimizing the netlist in simulation and then progressing to integrated circuit layout. Hand-designed netlists mostly do not contain all the mutual inductances between inductors. The lack of a complete set of mutual inductances can limit the accuracy of the designed netlist. For a circuit netlist to be an exact representation of the layout, the number of inductors should be equal to the number of fundamental cycles in the netlist graph and all inductors should be coupled. In this paper, we show that full-circuit inductance extraction of AQFP layout where self and mutual inductances are specified by the designer produces small but possibly significant errors due to mismatch between the design schematic and the layout. With compact simulation model extraction, which we added to the InductEx tool chain, a much more accurate simulation model that includes all mutual inductances can be obtained to verify circuit performance after layout. We propose compact model extraction as the final step in cell library characterisation.

Experimental Verification of Moat Design and Flux Trapping Analysis

Soft defects caused by flux quanta not captured by moats during superconductor integrated circuit cooldown are known to degrade circuit performance. However, haphazard or random moat placement does not necessarily improve circuit performance and may even degrade it. Under the IARPA SuperTools program we have both developed numerical simulation tools to extract simulation models of circuit structures in the presence of trapped fluxons and designed experiments to measure the probability of flux trapping in moats and the coupling of such trapped flux to circuit structures. Depending on moat structure, the coupling from a few moat-captured fluxons is shown to reduce the critical current for a SQUID by 20% or more, which justifies a thorough analysis. We present results for this very important aspect of magnetic rule checking and show how controlled flux trapping experiments in designated moats yield measurement results that fit simulated predictions very well. With the simulation tools validated, we show how flux trapping is incorporated into compact simulation models and we detail the extraction of magnetic coupling and the calculation of the compact models for both branch and loop-type simulations. We also show how phase-based simulation with the circuit simulator JoSIM allows arbitrary fluxon insertion in moats during transient circuit simulation and conclude with some recommended design rules for moat geometry, size, and placement.

A Spiking Recurrent Neural Network With Phase-Change Memory Neurons and Synapses for the Accelerated Solution of Constraint Satisfaction Problems

Data-intensive computing applications, such as object recognition, time series prediction, and optimization tasks, are becoming increasingly important in several fields, including smart mobility, health, and industry. Because of the large amount of data involved in the computation, the conventional von Neumann architecture suffers from excessive latency and energy consumption due to the memory bottleneck. A more efficient approach consists of in-memory computing (IMC), where computational operations are directly carried out within the data. IMC can take advantage of the rich physics of memory devices, such as their ability to store analog values to be used in matrix–vector multiplication (MVM) and their stochasticity that is highly valuable in the frame of optimization and constraint satisfaction problems (CSPs). This article presents a stochastic spiking neuron based on a phase-change memory (PCM) device for the solution of CSPs within a Hopfield recurrent neural network (RNN). In the RNN, the PCM cell is used as the integrating element of a stochastic neuron, supporting the solution of a typical CSP, namely a Sudoku puzzle in hardware. Finally, the ability to solve Sudoku puzzles using RNNs with PCM-based neurons is studied for increasing size of Sudoku puzzles by a compact simulation model, thus supporting our PCM-based RNN for data-intensive computing.

Radiation Effects on 1.7kV Class 4H-SiC Power Devices: Development of Compact Simulation Models

Compact simulation models of two key silicon carbide power components, the Junction Barrier Schottky diode and the power MOSFET, which are taking into account the effect of irradiation by highenergy electrons, were developed. Two 1.7 kV class devices: the 14 A JBS diode C3D10170H and the 5 A SiC power MOSFETs C2M1000170D produced by Wolfspeed were irradiated by 4.5 MeV electrons in the dose range up to 2000 kGy. Electrical characteristics were measured prior to and after irradiation. Radiation defects were studied by deep level transient spectroscopy and the effect of irradiation on device characteristics was established. SPICE models taking into account the irradiation fluence were proposed and calibrated using the parameters extracted from experiment. Simulated characteristics show a very good agreement with reality.

Robust Surface-Potential-Based Compact Model for GaN HEMT IC Design

We present an accurate and robust surface-potential-based compact model for simulation of circuits designed with GaN-based high-electron mobility transistors (GaN HEMTs). An accurate analytical surface-potential calculation, which we developed, is used to develop the drain and gate current model. The model is in excellent agreement with experimental data for both drain and gate current in all regions of device operation. We show the correct physical behavior and mathematical robustness of the model by performing various benchmark tests, such as DC and AC symmetry tests, reciprocity test, and harmonic balance simulations test. To the best of our knowledge, this is the first time a GaN HEMT compact model passing a range of benchmark tests has been presented.

Printed Organic Electronic Technology Platform Enabling the Design and Manufacturing of Integrated Circuits Towards Plastic Microprocessors

A dedicated printed electronics technology platform has been developed and implemented. The technology is devoted to the manufacturing of all-organic transistor devices with sub-micron feature size as multilayered structures, obtained through a sequential combination of deposition from solution and patterning steps through stamps. The manufacturing process includes fabrication of both rigid and flexible elastomeric stamps that are used in the development of fully printed devices and circuits on glass and plastic substrates. Moreover, to test the performance of printed electronic devices, a new compact simulation model has been developed taking into account the effect of contact resistance. Such a parameter acts as a key engineering parameter to enable access of polymer-based printed electronics to logic circuits running at relatively high speed, eventually associated with design solutions that allow achieving full rail-to-rail speed-up logic circuits and low power dissipation. Keywords: Organic electronics, nanoimprint lithography, soft lithography, inkjet printing, plastic computation

Compact Simulation Model of Non-air Conditioned Room and Estimation of Its Thermal Characteristics under Winter Conditions.

This study investigates thermal behavior of an occupied room exposed to winter weather conditions by means of quasi-steady-state model of the room. The space is not air-conditioned during the winter season, i.e. there is no humidity control and thermal performance of heaters maintains desired indoor air temperature. To obtain pure thermodynamic characteristics of the space, the model was set up and a series of tests was carried out in order to validate the mathematical model and find the thermal characteristics of the enclosure, which could be used directly for direct control techniques (DDC) if applied. The build -up model's method imposes boundary conditions onto room-faced surroundings walls and couples Fourier equations' thermal network employing modified Biot number. It also enables us to simulate an hourly energy use as well as heat flux calculus based on sub-hourly time steps. The model features a water equivalent content of the room, time-varying heat transfer coefficients, and boundary conditions onto surrounding walls, respectively. As a full dynamic method it accounts for thermal influence of outdoor climate conditions, occupancy use and other internal sources of thermal energy. The paper emphasizes selection of system boundaries and practical calculus of radiation heat exchanges without claiming shape factor algebra. The numerical results of temperature transient time responses obtained from mathematical model are well in accordance with those obtained from measurement in the actual room.

Simulation of mobile fading channels

Many aspects of a mobile radio system are basically determined by the propagation characteristics of the channel. Therefore, an understanding and good knowledge of mobile radio channels is essential for the analysis, design, and operation of wireless systems. It allows the successful development, evaluation, and testing of any current or future communication system, whether it is for cellular mobile telephony, for radio paging, or for mobile satellite systems. This article tries to present a simple and efficient way to simulate mobile channels for development and testing of mobile wireless systems, using some of the commercial circuit-analysis and simulation programs. So, in parallel with an overview of fading-channel propagation mechanisms and aspects, compact simulation models are given that can effectively be used for further analysis and understanding of the operation of mobile fading channels.