Electrothermal Power Cycling to Failure of Discrete Planar, Symmetrical Double-Trench and Asymmetrical Trench SiC MOSFETs

While SiC MOSFETs are now being utilized in industry their robustness under heavy-duty applications still remains a concern. In this paper, the results of experimental measurements of degradation to failure of different structured SiC power MOSFETs, namely the planar, symmetrical double-trench and asymmetrical trench structures are presented following electrothermal stressing by power cycling to beyond the safe operating area (SOA) limits. The tests are categorised in to subsets with/without forced cooling. The first set of tests involve successive switchings of the devices under constant DC current supply while their case temperature is monitored in real-time to evaluate their thermal performance. The symmetrical double-trench and asymmetrical trench MOSFETs are found to experience a higher case temperature rise thus prone to breakdown while failure is not observed in the planar structured device. The second experiment stresses the devices during continuous power cyclings with force cooling applied, in which the symmetrical and asymmetrical double-trench MOSFETs still encounter failure with detectable breakdown on the gate oxides, compared with the planar device which only exhibits degradation, without failure, with indications of aging

Measurements and review of failure mechanisms and reliability constraints of 4H-SiC Power MOSFETs under short circuit events

The reliability of the SiC MOSFET has always been a factor hindering the device application, especially under high voltage and high current conditions, such as in the short circuit events. This paper experimentally reviews the failure mechanisms caused by destructive short circuit impulses, and investigates the degradation patterns of key electrical parameters under repetitive short circuit events. The impact of test parameters on the short circuit reliability of SiC MOSFET has been analyzed. Approaches to characterize the electrical-thermal-mechanical stress during the short circuit period and advanced test methods are highlighted. Finally, the constraints from the standpoint of both manufacturers and users have been presented, including comparison of current SiC MOSFET devices, reliability evaluation of parallel SiC MOSFET devices, reliability improvement of the chip, performance improvement of protection circuits, and reliability assessment of SiC MOSFET devices under application-representative stress

FEM-based analysis of avalanche ruggedness of high voltage SiC Merged-PiN-Schottky and Junction-Barrier-Schottky diodes

Through comprehensive experimental measurements and TCAD simulation, it is shown that the avalanche ruggedness of SiC MPS & JBS diodes outperforms that of closely rated Silicon PiN diodes taking advantage of the wide-bandgap properties of SiC which leads to a high ionization and activation energy given the strong covalent bonds. Although the MPS diode structure favours a high reverse blocking voltage with small leakage current and a high current conduction, the localise current crowding caused by the multiple P+ implanted region leads to the avalanche breakdown at lower load currents than the SiC JBS diode. The results of Silvaco TCAD Finite Element modellings have a good agreement with the experimental measurements, indicating that SiC JBS diode can withstand the high junction temperature induced by avalanche in line with the calculated avalanche energy

Unclamped inductive stressing of GaN and SiC Cascode power devices to failure at elevated temperatures

In this paper, the ruggedness performance of GaN HEMT and SiC JFET devices in cascode configuration with a low voltage silicon power MOSFET has been evaluated experimentally. The impact of the bus voltage on the drain current and avalanche energy are investigated as well as the temperature sweep to enable analysis of the alternation of these parameters on the Unclamped Inductive Switching (UIS) ruggedness of cascode devices. The experimental measurements show that the GaN cascode devices have lower avalanche energy rating when compared with the closely rated SiC cascode devices just before the failure. SiC cascode devices can also withstand higher bus voltage in comparison to GaN cascode devices when under electrothermal stress by unclamped inductive switching. The analysis of transfer characteristics and leakage current of SiC JFET & GaN HEMT cascode structures following UIS stress have also been performed together with Computed Tomography (CT) Scan imaging to determine the per-area avalanche energy density

Design of 400 V Miniature DC Solid State Circuit Breaker with SiC MOSFET

Silicon carbide (SiC) metal-oxide-semiconductor field-effect transistors (MOSFETs) have the advantages of high-frequency switching capability and the capability to withstand high temperatures, which are suitable for switching devices in a direct current (DC) solid state circuit breaker (SSCB). To guarantee fast and reliable action of a 400 V DC SSCB with SiC MOSFET, circuit design and prototype development were carried out. Taking 400V DC microgrid as research background, firstly, the topology of DC SSCB with SiC MOSFET was introduced. Then, the drive circuit of SiC MOSFET, fault detection circuit, energy absorption circuit, and snubber circuit of the SSCB were designed and analyzed. Lastly, a prototype of the DC SSCB with SiC MOSFET was developed, tested, and compared with the SSCB with Silicon (Si) insulated gate bipolar transistor (IGBT). Experimental results show that the designed circuits of SSCB with SiC MOSFET are valid. Also, the developed miniature DC SSCB with the SiC MOSFET exhibits faster reaction to the fault and can reduce short circuit time and fault current in contrast with the SSCB with Si IGBT. Hence, the proposed SSCB can better meet the requirements of DC microgrid protection

Colorimetric quantification of aqueous hydrogen peroxide in the DC plasma-liquid system

The quantification of hydrogen peroxide (H2O2) generated in the plasma-liquid interactions is of great importance, since the H2O2 species is vital for the applications of the plasma-liquid system. Herein, we report on in situ quantification of the aqueous H2O2 (H2O2aq) using a colorimetric method for the DC plasma-liquid systems with liquid as either a cathode or an anode. The results show that the H2O2aq yield is 8–12 times larger when the liquid acts as a cathode than when the liquid acts as an anode. The conversion rate of the gaseous OH radicals to H2O2aq is 4–6 times greater in the former case. However, the concentrations of dissolved OH radicals for both liquid as cathode and anode are of the same order of tens of nM.</p