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Silicon Carbide JFETs with low on-state resistance are suitable for a number of high power applications. The static, dynamic and short circuit characterization of 600 V SiC Trench JFETs are reported in this paper. Typical JFETs fabricated with a 1.2 μm cell pitch had an on-resistance value around 40 mΩ and blocking voltages of ~600 V across the wafer. JFETs were successfully switched with a dc link voltage of 300 V, a current of 15 A and operating temperature of 125 °C. These JFETs were subjected to a short circuit condition with duration ranging from 10 μs to 45 μs at a dc link voltage of ~300 V, and operating temperatures of 25 °C and 125 °C. The device could withstand subsequent short circuit successfully without any failure at both 25 °C and 125 °C. The short circuit current showed consistent dependency on the applied gate voltage, when it was varied from 0 V to 15 V.

In this paper, robustness and reliability differences related to the performance of the gate oxide of commercially-available 1200 V-rated planar and trench SiC MOSFETs have been investigated. Due to a thin gate oxide in SiC MOSFETs and to a naturally imperfect interface of the oxide layer (SiO2) with the SiC material, its quality and reliability become very important and could be a limiting factor of the SiC technology when compared to the Si one. A dedicated gate oxide step-by-step (VG SbS) tester has been prepared during which the gate voltage is varied with different profiles. Results of Fowler-Nordheim (FN), Time Dependent Dielectric Breakdown (TDDB) and three test runs of the VG SbS are presented in this paper. Both technologies show good reliability figures to allow the use in the application. Trench technology shows higher robustness limits whereas the extrapolated reliability at the rated gate voltage is superior for the planar one.

The aim of this study is to investigate the main contributing factors to the degradation of the intrinsic body diode in SiC MOSFETs, caused by the expansion of stacking faults (SFs) from the substrate into the epitaxial layer, and how it affects their performance. Additionally, a comparison between DC forward current stress and surge current pulse stress is shown.

This paper presents a dynamic investigation of the body diode behavior of MOSFETs rated for 3.3kV applications. The body diodes of MOSFETs with different cell designs and pitch sizes have been used. The turn-off behavior of the body diode is compared to that of a 3.3kV JBS diode.

This work addresses the electrical behaviour of high-voltage (HV) SiC MOSFETs, being the main motivation to check their robustness. Large area (25 mm2) devices rated for 3.3 kV applications were fabricated with a special process for the gate oxide formation. The unit cell was designed to achieve good short-circuit performance. Static and dynamic characterization is presented at room and high temperature. Output curves and 3rdquadrant behaviour were analysed. Dynamic tests were performed at high bus voltages and high current. To check device robustness, short-circuit and power cycling’s were considered. Robustness test results put in evidence the achievement of reasonable good results obtained due to a suitable cell design.

The performance of 1.2kV SiC power MOSFETs is still hampered by the naturally imperfect SiC/SiO 2 MOS-interface. The correlated high density of interface traps results in threshold voltage (VTH) shifts and VTH-instabilities that must be carefully taken into consideration when designing SiC-based power electronics systems. The temperature dependent transient and threshold voltage hysteresis of commercially available 1.2 kV SiC MOSFETs from different manufacturers and technologies (planar, trench), are investigated in this contribution, together with their potential implications on the value of the drain current at the beginning of a short circuit event.

This paper presents for the first time an experimental investigation into the surge current capability of 6.5kV-rated SiC MOSFETs. The performance of both MOSFET’s body diode and its channel in the 3rd quadrant operation has been tested. Static measurements confirm that smaller pitches (14μm) provide lower voltage drops than larger ones (21μm). The 10ms half-sine surge measurements reveal that the body diode offers superior performance compared to 3rd quadrant channel operation. A short comparison versus Si technology is also attempted.

Despite the recent progress in SiC power MOSFET technology and its commercialization, the defective MOS interface still hampers the exploitation of the full potential of these devices. We present results using our high-k gate stack technology that shows significantly reduced density of interface states (D it ) along with superior threshold voltage (V TH ) stability for low voltage SiC power MOSFETs. The findings indicate virtually no V TH -shift during static characterization as function of the starting gate voltage and its ramp. Furthermore, dynamic switching results show virtually no threshold voltage shift for $V_{GS,start} \gt -12$V.

This paper presents an investigation into the performance of SiC JBS diodes rated for 6.5kV applications. For the active area layout, two hexagonal cell designs with different ASchottky/ATotal ratios have been considered. For completeness, the JBS performance is compared to that of SiC PiN diodes, fabricated on the same wafer. A benchmark against state of the art PiN diodes in Si technology is also provided.

SiC planar VDMOS of three voltages ratings (1.7kV, 3.3kV and 4.5kV) have been fabricated using a Boron diffusion process into the thermal gate oxide for improving the SiO2/SiC interface quality. Experimental results show a remarkable increase of the effective channel mobility which increases the device current capability, especially at room temperatures. At high temperatures, the impact of the Boron treatment is lower since the major contribution of the drift layer to the on-resistance. In addition, the intrinsic body diode characteristics approximate to that of an ideal PiN diode, and the blocking capability is not compromised by the use of Boron for the gate oxide formation.

This paper presents an investigation regarding the influence of the active area design on the static and dynamic performance of SiC JBS diodes. The analysis has been performed on fabricated JBS diodes, rated for 1.7kV applications. For the active area layout, both stripe and hexagonal cell patterns have been used for the implanted p+ regions.

Power conversion applications in the low voltage (LV) range (≤ 1.2 kV)—such as three-phase inverters—are required to operate at higher efficiencies, higher ambient temperatures, increasingly smaller form factor, and higher power density. Up to now, most research has focused on voltages up to 650 V for printed circuit board (PCB) embedded power electronics. This research evaluates a novel three-phase invertor module based on six insulated gate bipolar transistors and six diodes rated to 1.2 kV and 25 A each. This unique module is compared to the Semikron MiniSKiiP 23AC126V1. This paper considers some key details of the PCB embedding assembly process, a comparative switching performance assessment, measurement of thermal resistance, comparative lifetime, and electric insulation. First, a detailed outline of the package is presented including the top- and bottom-side metallization and the copper interconnect technology. The switching performances of both modules are compared for turn-ON and turn-OFF currents for a waveform at 600 V and 25 A at 150 °C. A finite-element-method thermal simulation demonstrates up to 44% lower thermal resistance for the PCB embedded package than that of the traditional wire-bonded direct bonded copper (DBC) package for an identical applied current and cooling condition. Furthermore, both packages are active power cycled to failure with the PCB embedded package demonstrating superior lifetime to the traditional DBC module. Finally, the maximum breakdown limit and the onset of partial discharge with the embedded PCB module are reported for both aged and non-aged conditions. The overall findings identify the promising application of PCB embedded power electronics for LV power conversion.

The static and dynamic performance of Silicon Carbide (SiC) MOSFET rated for 1200V applications has been investigated. MOSFETs with a planar design and several different cell pitches have been fabricated. Special attention has been dedicated to the channel design, where a novel retrograde doping profile has been employed. For reference, a more common box profile channel has also been used. Turn-off measurements under high current and over voltage conditions reveal that the MOSFET body diode offers wide safe operating area capability. The MOSFETs feature exceptional ruggedness against long short circuit events, with the retrograde channel designs able to withstand the $10\boldsymbol{\mu} \mathbf{s}$ industry standard specification.

In this study, an electrothermal compact model for SiC power MOSFETs is experimentally verified for the first time on a 3.3 kV device. Both the parameters determining the static behavior and those controlling the dynamic performances are calibrated over experimental data. The good agreement achieved proves the model scalability form 1.2 kV devices to 3.3 kV ones. Successively, to validate the good convergence properties of the model, an electrothermal simulation of a three-phase inverter consisting of 36 hard switched MOSFETs is performed.

We demonstrate the first integration of high-k/metal gate stacks in vertical 1.2kV SiC power MOSFETs including static and dynamic characterization as well as safe operation area (SOA). The high-k/4H-SiC MOS interface exhibits a remarkably low interface defect state density and improved threshold voltage stability compared to conventional gate stacks based on SiO 2 . Moreover, we achieved an impressive performance boost in terms of on-resistance due to this low-defective interface and increased gate capacitance. Compared to vertical devices with SiO 2 /poly Si gate stacks these devices exhibit a negligible hysteresis.

This paper reviews the recent progress of SiC MOSFETs rated above 3.3kV. The static and dynamic performance of 3.3 and 6.5kV-rated MOSFETs will be evaluated and benchmarked against similarly rated state-of-the-art Si IGBTs. A numerical comparison between high voltage (15kV) SiC MOSFETs and IGBTs will also be provided. The paper will also attempt to comment on the future challenges facing high voltage (HV) devices in SiC technology.

In this paper, we propose a novel method to extract the accurate junction temperature of an integrated gate commutated thyristor (IGCT) during device conduction (on-state mode), by measuring the gate–cathode voltage of the device. We have shown that the gate–cathode voltage is a function of anode current and junction temperature $T_{\mathrm{vj}}$ . Indeed, the gate–cathode voltage of the device can be easily accessed in real-time operation of the device from its gate-unit without the need of any external power supply or thermal sensors. The method has been tested by both the simulations (semiconductor device simulations) and experiments (static and load cycling tests) for two different types of IGCTs. This method will enable us to continuously monitor the $T_{\mathrm{vj}}$ of the device during real-time operation of the power electronic converter, and hence, to predict and evaluate the remaining lifetime of the device.

Electrically robust 6.5kV SiC MOSFETs are investigated for the static and dynamic performance, short circuit capability and safe operation area (SOA). SiC MOSFETs rated at 6.5kV were fabricated with different cell pitches from 12μm to 26μm that are able to withstand short circuit pulses of up to 8μs and have a turn-off SOA at 4400V up to twice the nominal current Inom. The paralleling of four MOSFETs was tested to represent a realistic setup while showing a substantial reduction in the switching loss by more than 80% compared to a silicon IGBT and Diode.

Recent advances and new trends in high voltage SiC based MOSFETs are analyzed. The main focus is done on design optimization strategies for reducing the on-state resistance. Gate oxide treatments for improving the interface quality resulting in a lower channel resistance are reviewed as well as solutions for lowering the JFET and bulk resistance components. The 3rd quadrant operation, short-circuit capability and switching performance are analyzed together with design strategies for their improvement. Finally, the limits of high voltage MOSFETs are outlined and future power devices to overcome the MOSFETs limits in ultra-high voltage applications are presented.

An approach to implement electrically robust MOSFETs in a functioning half-bridge will be investigated. For the first time, reverse conducting 3.3kV SiC MOSFETs have been fabricated with dilferent cell pitches from 14μm (p1.0) to 26μm (pl.8) that are able to withstand short circuit pulse of up to 10μs and a 9ms surge current event up to 15x the nominal current. LinPak half-bridge modules have been fabricated showing reduction of the switching loss by more than 90% compared to a silicon IGBT/diode half bridge.

This paper presents an experimental investigation of the dynamic performance of SiC 6.5kV JBS diodes. Using a hybrid Si SPT IGBT/SiC JBS diodes combination, we have analyzed the turn-off behavior limits of SiC JBS diodes and compared the result against a state-of-the-art Si PiN diode. The experimental results show that the JBS diodes can handle about 40A/chip at 125°C before going into thermal runaway. This maximum turn-off current value increases by about 50% when the diodes are operated at room temperature. The diodes dI/dt behaviour appear to be virtually independent of the DC-link voltage (at R G =18Ω). The comparison between turn-off curves for 6.5kV SiC and Si diodes shows that the use of SiC JBS diodes reduces the reverse recovery losses by more than 98%.

A novel method is presented for online estimation of the junction temperature (Tj) of semiconductor chips in IGBT modules, based on evaluating the gate-emitter voltage (Vge) during the IGBT switch off process. It is shown that the Miller plateau width (in the Vge waveform) depend linearly on the junction temperature of the IGBT chips. Hence, a method can be proposed for estimating the junction temperature even during converter operation – without the need of additional thermal sensors or complex Rth network models. A measurement circuit was implemented at gate level to measure the involved time duration and its functionality was demonstrated for different types of IGBT modules. A model has been proposed to extract Tj from Vge measurements. Finally, an IGBT module with semiconductor chips at two different temperatures has been measured using Vge method and this method was found to provide the average junction temperature of all the semiconductor chips.

Recent availability of large SiC wafer with reduced density of defects and maturity of our fabrication process permitted to fabricate 15A-5kV W-JBS (25 mm2) and 15A-5kV PiN (10 mm2) diodes on 4 wafers. We will present and compare their static characteristics. Several W-JBS diodes have been packaged and switched at 2.5kV to study their reverse recovery and demonstrate the major advantages of the SIC-JBS devices at high voltage.

We present a new concept of a high-current SiC power module with the fast switching capability based on a stacked-ceramic-substrate structure. This approach enables to parallel many small area SiC devices in a housing of a Si half-bridge module. The internal design of the module — concept demonstrator was optimized using electromagnetic simulations in order to minimize stray inductance and balanced current sharing. The prototype was assembled exploiting conventional packaging technologies. Performance of the assembled module was tested by a double-pulse measurement test in order to determine switching losses and verify simulated stray inductance.

A new process based on Boron diffusion step to improve the SiO2/SiC interface quality is presented in this work. Surprisingly, Boron, a p-type dopant and small size atom, generates similar apparent improvements as previous oxide treatments based on large size atoms, n-type or deep levels dopants. This process has been applied to a thermal oxide grown to fabricate large area (up to 25mm2) 4.5kV 4H-SiC VDMOS. Fabricated devices show a significant improvement in terms of channel effective mobility, on-resistance, and 3rd quadrant behavior in comparison with counterparts without Boron oxide treatment.

This paper reports a new edge termination for SiC power semiconductors. The novel concept, termed JTE (Junction Termination Extension) rings, combines the advantages of two classical termination techniques, namely floating p+ rings and JTE, to create a more efficient and robust edge termination. The new concept has been applied to large area (5×5mm2) Junction Barrier Schottky (JBS) diodes rated for 1.7kV applications. Both numerical and experimental results of the new concept are presented. Dynamic measurements, where the main switch was a Si IGBT, show that the JTE rings concept offers similar performance to JTE edge design, however, with a 30% area reduction.

Lifetime prediction of IGBT modules from their junction temperature is an important aspect to improve the reliability of power electronic systems. Here, methods to estimate the IGBT junction temperature from its electrical characteristics are discussed. A solution is also proposed to avoid explosion of IGBTs used in traction converters.

This paper discusses an elaborated study about the design of Junction-Barrier Schottky (JBS) diodes regarding the width (w) and spacing (s) of the implanted p+ pattern, utilizing epitaxial drift-layer specifications (4H-SiC) suitable for 1.7 kV applications. The impact of the w/s design-ratio on the blocking characteristics, the unipolar ON-state performance as well as moderation of surge current events are investigated. Finally, we report experimental results on successfully manufactured 1.7 kV JBS power-rectifiers demonstrating the practical validity of our numerical approach.

This paper studies experimentally the benefits of silicon carbide based power semiconductor technology in a low-voltage grid connected three-phase three-wire pulse width modulated rectifier. The power semiconductor module used in the study is a custom-made 1.2-kV 100-A fully silicon carbide based half-bridge type module designed for fast switching speeds and high temperature operation. The experimental tests are carried out with a 40-kVA prototype system built in the frame of a commercial low-voltage motor drive unit. In addition, the impact of the high switching speeds enabled by the silicon carbide based semiconductor devices on conductive electromagnetic emissions are also investigated. The results show that the conversion efficiency can be significantly improved with silicon carbide compared to the state-of-the-art silicon based semiconductor technology. As a drawback, the faster switching speeds increase the conductive electromagnetic emissions to some extent.

A novel method using gate overdrive is suggested to avoid explosion of IGBT modules in converters. With this method, the gate drive impedance is set to low (∼0 Ω), such that the driving capability of the gate drive is not limited by the short-circuit present between the gate and auxiliary emitter terminals of a damaged IGBT. Using the implemented gate driving concept, the fault current can be redirected through good chips in the module and the current concentration in the faulty chip of the IGBT module could be reduced to avoid explosion.

The paper presents the feasibility of using gate-emitter voltage during IGBT turn-off in estimating the junction temperature of semiconductor chips in IGBT modules in real-time application. It is shown that the chosen parameter has negligible module and measurement circuit variation once calibrated and has been implemented successfully in a converter.

An innovative power electronics half-bridge module concept exploiting 3D-design features was proposed to achieve low stray inductance and balanced current sharing, and thus module fast switching capability. In order to verify the switching performance of the concept, a 1.2 kV / 100 A full SiC module was designed using electromagnetic simulations and fabricated exploiting state-of-the-art but still conventional packaging technologies. Afterwards the module was tested and benchmarked to commercially available SiC modules. Performed tests confirmed fast switching capability of the proposed concept and showed more than 20 % lower switching losses compared to the benchmarked commercial modules.

The paper presents a gate driver for current-control power semiconductor devices such as BJT. The gate driver has a capability to reduce switching time duration of a power transistor, both in turn-on and turn-off transients. Besides, when the transistor is in static conduction periods, the driver gives a high driving current to the power transistor with holding up by a low supply voltage. This leads to reduce power losses of the driver and switching losses of the transistor. Then, an efficient switching process happens with the whole power switching unit. The paper provides PSpice simulated switching results using a manufacturer provided 1.2kV SiC BJT model to confirm the feasibility of the proposed driver and compare it with a conventional unipolar driver. The results are in good agreement with the theoretical prediction.

This paper presents a 1200-V 20-A full silicon carbide boost chopper module designed for high temperature and high frequency operation. The developed module is based on one silicon carbide metal oxide semiconductor field effect transistor chip and two parallel connected silicon carbide schottky diode chips manufactured by Cree, Inc. The static and dynamic characteristics of the module have been experimentally determined and its performance tested in a 2-kW boost converter. The test results show that the developed module performs well and is able to provide a good conversion efficiency even at high switching frequency.

Medium-voltage (MV) high-power converters are usually realized using high-voltage semiconductors (3.3kV, 4.5kV or 6.5kV) operated with low-switching frequencies in the range of several hundred Hz and under hard-switching conditions. However, for medium-voltage high-power DC-DC converters employing transformer for galvanic isolation, it is attractive to increase switching frequency in order to reduce the transformer size. Therefore, it is usually required to consider the use of some sort of soft-switching method. Recently, DC-DC LLC resonant converters are gaining momentum, but are usually considered for low-voltage applications utilizing unipolar devices (MOSFETS). In this paper, switching properties of a medium-voltage bipolar semiconductor (6.5kV IGBT) are analyzed for a high-power LLC resonant converter. Experimental results are presented to illustrate the characteristic operating conditions, highlighting interactions between semiconductors and circuit properties, which both must be simultaneously considered, in order to achieve best utilization of a high-voltage semiconductor operating at higher switching frequencies.