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We report the development of a process/device simulation platform to model superconductor electronics. The process simulator leverages the back-end modeling capabilities of Florida object-oriented process/device/reliability simulator (FLOOXS) and builds on the existing models to simulate processes specific to Josephson junction (JJ) fabrication. The device simulator uses the process generated models and computes the normal-state electrical properties of a Nb/Al-AlO/Nb JJ. It is used to predict key operational figures of merit and how they vary with changes in process models. By integrating the process and device simulation tools, this research aims to offer an environment for the simulation of JJ circuits. [ABSTRACT FROM AUTHOR]

By modeling the propagation of a seed layer with various crystal orientations, this study explores the influence of process variations on grain formation with the help of a physics-based process simulator. Grain boundaries allow easy diffusion of foreign atoms through the lattice, which causes Al to move inside the Nb bottom electrode layer and more interestingly, O to penetrate through the Al layer during oxidation and create a barrier with non-uniform thickness. In addition to thickness variations, the grain structure exhibited by Nb and Al can cause significant suppression of supercurrent at the boundaries depending on the degree of lattice mismatch, impurity deposition, etc. This work details the process simulation of grain boundary formation and aims to provide geometrical models that may be used in the simulation of device performance to account for process-induced variations. [ABSTRACT FROM AUTHOR]

Some packaging technologies of electronic devices introduce compressive biaxial stress and variable vertical stress. In unipolar MOS devices, stress variations typically only linearly affect drain current via carrier mobility. Collector currents of bipolar devices are additionally affected by variations in intrinsic carrier concentration. This leads to increased variability of key device parameters in the compressive stress regime. Reducing package-induced compressive stress, or inducing tensile stress, should improve device variability due to local stress variations. [ABSTRACT FROM AUTHOR]

TCAD has been a useful tool for device design for decades. Radiation damage of devices requires accurate simulation of how charges move and are trapped, and the trap populations. This paper describes a simulation capability for these classes of problems and provides examples demonstrating its usefulness for investigation of device failure. [ABSTRACT FROM AUTHOR]

A flipped-classroom approach was implemented in a Circuits I class for electrical and computer engineering majors to lower its high attrition and failure rate. Students were asked to watch online lectures and then come to class prepared to work problems in small groups of four. The attitude, retention, and performance of students in the flipped group in Spring 2013 were compared to those for the traditionally taught group in Fall 2012. The Fall 2012 lectures were recorded, so that each group saw the same lectures. Student retention and test performance was significantly higher in the flipped course. In Fall 2012, 56% of the initially enrolled students received a C or better. In Spring 2013, this improved to 83%. The first exam scores were significantly better in Spring 2013, and this helped with student success. The authors believe that it was the alignment of online lectures, face-to-face student/teacher and peer/peer interactions, combined with the active learning component of the flipped classroom that led to these improvements . [ABSTRACT FROM AUTHOR]

A combination of TRIM and FLOODS models the effect of radiation damage on AlGaN/GaN HEMTs. While excellent fits are obtained for threshold voltage shift, the models do not fully explain the increased reliability observed experimentally. In short, the addition of negatively-charged traps in the GaN buffer layer does not significantly change the electric field at the gate edges at radiation fluence levels seen in this study. We propose that negative trapped charge at the nitride/AlGaN interface actually produces the virtual-gate effect that results in decreasing the magnitude of the electric field at the gate edges and thus the increase in critical voltage. Simulation results including nitride interface charge show significant changes in electric field profiles while the I-V device characteristics do not change. [ABSTRACT FROM PUBLISHER]

A model for radiation-induced interface-trap buildup distinguishes among the contributions of hydrogen dimerization, electron recombination, and electric field mechanisms, quantitatively explaining time-dependent and true dose rate effects in irradiated bipolar isolation oxides. Hydrogen dimerization is the dominant ELDRS mechanism for devices exposed to medium \ H2 concentrations (1% per volume), whereas \ H2 cracking dominates as \ H2 concentration is increased further. Electron recombination mechanisms contribute at high dose rates (> 100~\ rad(\ SiO2)/{\ {s}}), but are not the dominant ELDRS mechanism at dose rates lower than 100 \ rad(\ SiO2)/{\ {s}}). [ABSTRACT FROM AUTHOR]

Electronic structure calculations and irradiation measurements are used to obtain insight into oxide trapped charge mechanisms in varying hydrogen ambients. Quantitative agreement between measured and simulated oxide and interface-trap charge densities is obtained over a wide range of H2 concentrations by implementing first-principles calculations of the energetics, and dynamics of charge transport and trapping, into TCAD simulations of irradiated MOS structures. Hole trapping dominates for typical H2 densities, but protons can dominate at high H2 densities. The rate of the interface trap reaction, in which protons that are liberated from charged oxygen vacancies by molecular hydrogen form dangling bonds on the interface, is found to play a key role in determining the relative concentrations of oxide and interface-trap charge densities. [ABSTRACT FROM AUTHOR]

A physics-based TCAD model for enhanced low-dose-rate sensitivity in linear bipolar devices is developed. Quantitative agreement is found with measured data over a wide range of dose rates and H2 concentrations. Analysis of the degradation effects of individual defect types, the implementation of which has been informed by first principles calculations, provides insights into the mechanisms behind enhanced low-dose-rate effects in different hydrogen environments. The effects of initial defect concentration and location and the energetics of the defect-related reactions are explored. Conclusions are drawn about the roles of molecular hydrogen and hydrogenated defects in the radiation response of these devices. [ABSTRACT FROM PUBLISHER]

An adaptive grid scheme for single-event upset device simulations is presented. Single-event transient simulations for a reverse-biased N+/P diode and nMOSFET were performed using the adaptive grid scheme, a customized grid scheme and a uniform grid scheme. Results show that adaptive gridding can offer significant simulation time savings while preserving accuracy. [ABSTRACT FROM AUTHOR]

The results of semiconductor device simulations are highly dependent on the electron and hole mobility models. The manner in which mobility is modeled at high-injection levels is especially important for single-event upset simulations due to the large number of electron-hole pairs generated along a particle strike path. This paper presents an approach to modeling mobility that describes majority and minority carrier mobility, carrier-carrier scattering, and temperature dependence in a computationally efficient form relevant for radiation effects simulations in silicon. [ABSTRACT FROM AUTHOR]

Laser-induced current transients are measured on uniaxially stressed silicon (Si) N-f/P diodes using a high speed measurement system. Controlled external mechanical stress along the <110> direction is applied via a four-point bending jig while the samples are irradiated using a cavity-dumped dye laser with a wavelength of 590 nm. A decrease in the peak current is observed for increasing tensile stress applied to the diode. Unlike tensile stress, compressive stress increases the peak current. Charge collection is observed to decrease with tensile and increase with compressive stress. These results suggest that uniaxial mechanical stress alters the current transients due to strain-induced changes in electron mobility along the <001> direction. The average effective electron mass along the <001> direction increases with tensile and decreases with compressive stress resulting from the splitting of de- generate conduction band valleys and the repopulation of electrons from higher to lower valleys. The Florida object oriented device simulator (FLOODS) is used to explain the mechanism of current transients in unstressed and stressed diodes. FLOODS is also used to predict results for values of applied stress (∼ 1 GPa) beyond those that can be obtained using the bending jig (∼ 240 MPa). [ABSTRACT FROM AUTHOR]

In this paper, we present measurements and simulation of random telegraph signal (RTS) noise in n-channel MOSFETs under periodic large signal gate-source excitation (switched bias conditions). This is particularly relevant to analog CMOS circuit design where large signal swings occur and where LF noise is often a limiting factor in the performance of the circuit. Measurements show that, compared to steady-state bias conditions, RTS noise can decrease but also increase when the device is subjected to switched bias conditions. We show that the simple model of a stationary noise generating process whose output is modulated by the bias voltage is not sufficient to explain the switched bias measurement results. Rather, we propose a model based on cyclostationary RTS noise generation. Using our model, we can correctly model a variety of different types of LF noise behavior that different MOSFETs exhibit under switched bias conditions. We show that the measurement results can be explained using realistic values for the bias dependency of τ[sub c] and τ[sub e]. [ABSTRACT FROM AUTHOR]

Carrier trapping via tunneling into the gate oxide was implemented into a partial differential equation -based semiconductor device simulator to analyze the 1/f-like noise in silicon MOSFETs. Local noise sources are calculated using the carrier tunneling rates between trap centers in the oxide and those at the interface. Using the Green's transfer function approach, noise contributions from each node in the oxide mesh to the overall noise at the specified contact terminals are simulated. Unlike traditional 1/f noise analyses in MOSFETs, the simulator is capable of simulating noise for a wide range of bias voltages and device structures. The simulation results show that for an uniformly doped channel, the region in the oxide above the pinch-off point in saturation is most critical for low frequency noise generation while for a graded channel device the source side of the gate oxide region becomes important. By comparing the simulation results with the measured noise data, the oxide defect density in the noise producing regions can be profiled. [ABSTRACT FROM AUTHOR]

Integrating the entire system on a chip (SOC) is one of the main challenges for many researchers all over the world. One of the major breakthroughs toward achieving this goal has been the ability to manufacture multiple gate oxides for different requirements on the same chip. The most attractive of the techniques currently in the literature is the implantation of nitrogen in silicon, which can be used to achieve the goal of multiple gate oxide thickness. The rate of oxidation depends on the amount of nitrogen incorporated at the silicon/silicon oxide interface. By modulating the amount of nitrogen incorporated at the interface, the rate of oxidation and hence the oxide thickness can be moderated. This paper reviews the diffusion, oxidation, and device issues pertaining to the use of nitrogen implants in silicon and also compares it to other implant-based techniques related to the achievement of multiple oxide thickness across the chip for SOC integration. [ABSTRACT FROM AUTHOR]

Presents a study that investigated nonmelt laser annealing (NLA) for the formation of ultrashallow, heavily doped regions. Information on boron multipulse laser annealing; Discussion of the change in sheet resistance as the laser energy is increased; Effect of the NLA on the defect evolution.

Presents a study which investigated the small-signal voltage and distributed effects in the polysilicon and intrinsic base regions of long stripe bipolar junction transistors at high frequencies. Methodology; Results and discussion; Conclusions.

Introduces an algorithm for faster full-thermodynamic device simulations. Three semiconductor equations solved by the traditional drift-diffusion (DD) transport model in device simulations; Where the algorithm is implemented; Details of the experiment; Results; Conclusion.

Reports on the modeling of generation-recombination noise associated with bulk defect levels in silicon in a partial differential equation-based device simulator to study the maximum allowable defect density that guarantees generation-recombination noise-free operation in the presence of hot-carrier effects and space-charge injection.