L. Di Benedetto

An Analytical Model of the Switching Behavior of 4H-SiC p

An analytical model of the switching behavior of SiC diodes is presented. The model gives an accurate description of the current and voltage transient for a wide range of reverse to forward current ratios and allows one to evaluate the spatial-temporal distributions of carriers density, current components and electric field along the base at a generic instant of the whole transient. Using this model, a large-signal circuit is derived that is useful for circuital analysis of diode under generic operation conditions. The accuracy of the model is verified by comparisons with numerical simulations and experimental results.

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An optimized tradeoff between blocking voltage and specific ON-resistance for 4H-silicon carbide power vertical double-implanted metal-oxide-semiconductor field-effect transistor (DMOSFET) is exclusively obtained as a function of doping concentration in the drift region. Based on a novel analytical model of the electric field in the gate oxide of 4H-SiC DMOSFETs, we propose a closed-form equation of the Junction FET (JFET) region width and the drift thickness as function of doping concentration without using fitting and empirical parameters to obtain the maximum figure of merit. Model results are successfully verified with TCAD numerical simulations, covering a wide range of device performances, and experimental results.

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A model of the potential barrier in the channel of normally-off 4H-SiC JFETs is shown. It allows to evaluate the barrier height and the minority carrier density in the center of the channel for an arbitrary geometry and bias condition. The validity of the model is justified by comparing the model with numerical simulations carried out on various channel topologies.

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The performance of a 4H-SiC Schottky diode for thermal sensing in the wide temperature range from T = 85 up to 443 K is presented. The linear dependence on temperature of the forward voltage drop, for different bias currents, is investigated through an analytical study of the temperature-dependent physical Schottky diode parameters. A high sensitivity of 1.18 mV/K was observed for a constant bias current of ID = 80 μA. The device exhibits a good degree of linearity with a calculated root mean square error, with respect to the best-linear fitting model, lower than 2.7 mV. Moreover, the proposed sensor shows a good repeatability maintaining a stable output over more cycles of measurements, from (down to) 85 up to (from) 443 K, in a long period of time.

Diodes from Arbitrary Injection Conditions

A proportional to absolute temperature sensor (PTAT) based on V₂O₅/4H-SiC (divanadium pentoxide/4H polytype of silicon carbide) Schottky diodes is presented. The linear dependence between the voltage differences across two constant-current forward biased diodes on temperature has been used for thermal sensing in the wide temperature range from T=147 K up to 400 K. A sensitivity of 307 μV/K was calculated for two constant bias currents, I_D1=16 μA and I_D2=608 μA.

Optimized Design for 4H-SiC Power DMOSFET

The Gabor filter has gained an important agreement in multimedia processing and visual search applications for its good spatial frequency and position selectivity, notwithstanding its heavy computational load. For these reasons, Gabor filters find useful applications in the processing of medical images, aiming to enhance the original image and to overcome issues related to noise and artifacts. With the purpose to find the optimal design of a Gabor filter to be implemented in ASIC and FPGA platforms, in this work three architectures are presented, representing the best trade-offs for accuracy, area and power constraints. A comparative study among the proposed architectures in terms of allocation of the resources, power dissipation and timing performances is presented, which reveals useful for an informed choice depending on the particular application. The designs have been implemented on a FPGA-based ASIC prototyping system, which returns a maximum operating frequency of 172 MHz for the best case. Synthesis with 90nm CMOS standard cell returns a maximum frequency of 350 MHz. Therefore, the fastest architecture processes 83 and 168 Full-HD (1920×1080 pixels) frames-per-second, respectively for a FPGA and an ASIC implementation, which, to the best of our knowledge, is the current state-of-the-art.

A model of the voltage barrier in the channel of 4H-SiC normally-off JFET's

In this paper we report the experimental results of lateral 4H-SiC UV p-i-n photodiodes, whose p-type anode and n-type cathode regions are made by Aluminum and Nitrogen, respectively, ion-implantation. The dark reverse current is −31.5pA at −10V and increases at −1.24nA under 320nm UV radiation with an optical power at the surface of the device equal to 7.5nW. The peak of the responsivity is 0.074A/W at 0V and 0.169AAV at −10V for 320nm, corresponding to an external quantum efficiency of, respectively, 30% and 69%. Respect to other proposed photodiodes, our devices are fully compatible with standard 4H-SiC device process fabrication and they can be easily integrated in an electronic circuit.

85–440 K Temperature Sensor Based on a 4H-SiC Schottky Diode

An analytical tool to design 4H-SiC power vertical Double-diffused Metal-Oxide-Semiconductor Field-Effect-Transistor is proposed. The model optimizes, in terms of the doping concentration in the Drift–region, the trade–off between the ON–resistance, RON, and the maximum blocking voltage, VBL, that is the Drain-Source voltage for which the avalanche breakdown appears at the p+–well/n-DRIFT junction together with the breakdown of the Gate oxide. Finding such trade-off means to maximize, Figure-Of-Merit. Our results are based on a novel full–analytical model of the electric field in the Gate oxide, EOX, whose generality is ensured by the absence of fitting and empirical parameters. Model results are successfully compared with 2D–simulations covering a wide range of device performances.

V2O5/4H-SiC Schottky diode as a high performance PTAT sensor

A circuital model of 4H-SiC p+-n-n+ diodes is presented, which is able to describe the switching behaviour of the devices in a wide range of current, voltage and temperature, at an arbitrary instant, with comparable accuracy of numerical simulations. The model has been analytically derived under generic conditions and is capable to calculate also the dynamic spatial distribution of minority carriers in the epitaxial layer. The accuracy of the model is shown by comparison with numerical simulations and experimental measurements.