On the robustness of ultra-high voltage 4H-SiC IGBTs with an optimized retrograde p-well

The robustness of ultra-high voltage (>10kV) SiC IGBTs comprising of an optimized retrograde p-well is investigated. Under extensive TCAD simulations, we show that in addition to offering a robust control on threshold voltage and eliminating punch-through, the retrograde is highly effective in terms of reducing the stress on the gate oxide of ultra-high voltage SiC IGBTs. We show that a 10 kV SiC IGBT comprising of the retrograde p-well exhibits a much-reduced peak electric field in the gate oxide when compared with the counterpart comprising of a conventional p-well. Using an optimized retrograde p-well with depth as shallow as 1 μm, the peak electric field in the gate oxide of a 10kV rated SiC IGBT can be reduced to below 2 MV.cm -1 , a prerequisite to achieve a high-degree of reliability in high-voltage power devices. We therefore propose that the retrograde p-well is highly promising for the development of>10kV SiC IGBTs

Optimal edge termination for high oxide reliability aiming 10kV SiC n-IGBTs

The edge termination design strongly affects the ability of a power device to support the desired voltage and its reliable operation. In this paper we present three appropriate termination designs for 10kV n-IGBTs which achieve the desired blocking requirement without the need for deep and expensive implantations. Thus, they improve the ability to fabricate, minimise the cost and reduce the lattice damage due to the high implantation energy. The edge terminations presented are optimised both for achieving the widest immunity to dopant activation and to minimise the electric field at the oxide. Thus, they ensure the long-term reliability of the device. This work has shown that the optimum design for blocking voltage and widest dose window does not necessarily give the best design for reliability. Further, it has been shown that Hybrid Junction Termination Extension structure with Space Modulated Floating Field Rings can give the best result of very high termination efficiency, as high as 99%, the widest doping variation immunity and the lowest electric field in the oxide

Estimating and validating the interbeat intervals of the heart using near-infrared spectroscopy on the human forehead

In studies with near-infrared spectroscopy, the recorded signals contain information on the temporal interbeat intervals of the heart. If this cardiac information is needed exclusively and could directly be extracted, an additional electrocardiography device would be unnecessary. The aim was to estimate these intervals from signals measured with near-infrared spectroscopy with two novel approaches. In one approach, we model the heartbeat oscillations in these signals with a Fourier series where the coefficients and the fundamental frequency can continuously change over time. The time-dependent model parameters are estimated and used to calculate the interbeat intervals. The second approach uses empirical mode decomposition. The signal measured with near-infrared spectroscopy is empirically decomposed into a set of oscillatory components. The sum of a specific subset of them is an estimate of the pure heartbeat signal in which the diastolic peaks and consequential interbeat intervals are detected. We show in simultaneous electrocardiography and near-infrared spectroscopy measurements on 11 subjects (8 men and 3 woman with mean age 32.8 ± 8.1 yr), that the interbeat intervals (and the consequential pulse rate variability measures), estimated using the proposed approaches, are in high agreement with their correspondents from electrocardiography

Reproducibility and sensitivity of detecting brain activity by simultaneous electroencephalography and near-infrared spectroscopy

The aims were (1) to determine the sensitivity and reproducibility to detect the hemodynamic responses and optical neuronal signals to brain stimulation by near-infrared spectroscopy (NIRS) and evoked potentials by electroencephalography (EEG) and (2) to test the effect of novel filters on the signal-to-noise ratio. This was achieved by simultaneous NIRS and EEG measurements in 15 healthy adults during visual stimulation. Each subject was measured three times on three different days. The sensitivity of NIRS to detect hemodynamic responses was 55.2% with novel filtering and 40% without. The reproducibility in single subjects was low. For the EEG, the sensitivity was 86.4% and the reproducibility 57.1%. An optical neuronal signal was not detected, although novel filtering considerably reduced nois

Modelling and filtering almost periodic signals by time-varying fourier series with application to near-infrared spectroscopy

We propose a new approach to modelling almost periodic signals and to model-based estimation of such signals from noisy observations. The signal model is based on Fourier series where both the coefficients and the fundamental frequency can continuously change over time. This signal model can be represented by a factor graph which we use to derive message passing algorithms to estimate the time-dependent model parameters from the observed samples

Retrograde p-well for 10kV-class SiC IGBTs

In this paper, we propose the use of a retrograde doping profile for the p-well for ultrahigh voltage (>10 kV) SiC IGBTs. We show that the retrograde p-well effectively addresses the punchthrough issue, whereas offering a robust control over the gate threshold voltage. Both the punchthrough elimination and the gate threshold voltage control are crucial to high-voltage vertical IGBT architectures and are determined by the limits on the doping concentration and the depth that a conventional p-well implant can have. Without any punchthrough, a 10-kV SiC IGBT consisting of retrograde p-well yields gate threshold voltages in the range of 6-7 V with a gate oxide thickness of 100 nm. Gate oxide thickness is typically restricted to 50-60 nm in SiC IGBTs if a conventional p-well with 1×10 17 cm -3 is utilized. We further show that the optimized retrograde p-well offers the most optimum switching performance. We propose that such an effective retrograde p-well, which requires low-energy shallow implants and thus key to minimize processing challenges and device development cost, is highly promising for the ultrahigh-voltage (>10 kV) SiC IGBT technology

Spectral Analysis and Dynamical Behavior of Complex Networks

Power point presentation for International Workshop on Complex Systems and Networks, Melbourne, Australia, Sept. 2011

Understanding Communication Networks

A PowerPoint from keynote talk at the 9th IEEE International Conference on Networking, Sensing and Control (ICNSC 2012), Beijing, China, April 2012

Proposal of Real-Time Echocardiogram Transmission Based on Visualization Modes with WiMAX Access

This study presents a new approach to improve the echocardiogram transmissions over WiMAX networks. Using a compression method based on visualization modes and a reliable method that adapts to the channel conditions, overall performance results are improved compared to classical approaches. The echocardiogram transmission using a compression method based on visualization modes requires lower bandwidth than without considering visualization modes. Furthermore, if the proposed reliability method is also used, the echocardiogram is more often visualized with adequate clinical quality than compressing the echocardiogram without distinguishing the visualization modes and without using a reliability method for the available dataset. The reduction in the bandwidth ranges from 29 kbps to 166 kbps for the simulated scenarios. 1