High-current, large-area single SiC JBS diodes rated at 650V-200A and 1200V-100A were fabricated on a 150mm platform that demonstrate a low V F of 1.5V. The diodes exhibit a specific differential resistance, R diff, sp , of 0.74 and 1.65 mΩ-cm 2 , respectively. The devices were tested with similarly rated Si-IGBTs and the reduction in switching losses and QRR evaluated. The high-current diodes have also been fabricated with solderable topside metals for enhanced packaging and were tested with double-sided cooling to quantify the benefits. One primary target application is for direct replacement of Si diodes in EV & HEV traction drives.

We investigated selective etching of SiC in molten KOH + NaOH + Na 2 O 2 mixtures in application to defect analysis. Etch rate was measured as a function of etchant composition, temperature and other process variables. Optimal etching conditions were established for reliable differentiation between TSDs, TEDs, BPDs and stacking faults (SF).

This paper presents benefits of using 650 V SiC cascodes to realize a 1.5 kW single phase, continuous conduction mode (CCM) totem-pole, bridgeless power factor correction (PFC) AC/DC converter switching at 100 kHz. By exploiting the excellent switching and conduction performance of SiC cascodes, the compatibility with a 12 V gate drive and synchronous rectification of the full-bridge, a very high peak efficiency of 98.6% is achieved for this AC/DC converter at high line (230 V) AC input with 400 V DC output. With correct digital control of the full-bridge gate signals the inductor current spike at zero-crossing is significantly reduced and a total harmonic distortion (THD) of 1.83% is achieved at high line near full load.

The SiC normally-on JFET is a new member in the family of power devices. It is reliable and robust under high-temperature and high-voltage harsh operatioing conditions due to its pn-junction gate control and the excellent physical and electrical properties of Silicon Carbide. At present, 1200V SiC normally-on JFETs are commercially available and higher voltage JFETs are still under development. There is a strong need for a medium-voltage 4kV-15kV power switch that can be moved into mass production quickly, exploits all the material advantages of SiC technology, and is cost-effective. This work presents an innovative method to realize such a high voltage power switch by series-connecting low voltage SiC normally-on JFETs using a unique circuit topology. This work focuses on the discussions of the operation principle and the experimental demonstrations of the proposed technique.

United Silicon Carbide, Inc. (USCi) has developed a novel low-loss 6.5kV enhancement-mode SiC JFET chipset to address transformerless grid-tie, variable frequency drives (VFD) for industrial motors, heavy vehicle motor traction and other high DC-link voltage applications. The JFET devices demonstrate excellent switching losses, approximately ~20X less than 6.5kV Si-IGBTs. The new JFET devices were packaged along with 6.5kV rated SiC JBS diodes in a half-bridge configuration to form an all-SiC high temperature power module rated at 60A. The module performance parameters vs. temperature were evaluated and are presented. Turn-on and turn-off behavior of the module and the nature of paralleling enhancement-mode JFETs are presented. The power modules were tested in a buck converter where switching a bus voltage of 3.3kV at 10kHz and 15kHz was achieved and module power losses estimated. The fast-switching medium voltage SiC module can have a large impact on reducing system components and targets next generation power conversion systems seeking higher power densities.

The SiC cascode switch integrates the advantages of a Si MOSFET and the excellent high voltage, high frequency and high temperature properties of the SiC normally-on JFET. It has a normally-off operation mode, simple gate drive, and a reliable MOS gate without the threshold voltage drift. These superior features make the SiC cascode device the best candidate for realizing a "smaller, faster and cheaper" power conversion system. The cascode can be constructed in discrete configuration or in stack configuration. In this work, the switching performance, short-circuit withstand capability and unclamped inductive switching (UIS) capability of 1.2kV SiC discrete and stack cascodes are investigated by performing experiments and numerical simulations. Simulation results show that the silicon MOSFET in the stack cascode does not limit the short circuit and UIS capabilities of the stack cascode.

This paper evaluates the static and dynamic characteristics of a 1.2kV SiC stack-cascode at junction temperatures (T j ) up to 200°C. The experimental results show that, at T j = 200°C, the SiC stack-cascode can be switched stably under a 600V-17A inductive load condition and can withstand an avalanche current of 13A for 9μs (Eav = 116mJ) for a 1.5mH load inductor. The SiC stack-cascode has no degradation in on-resistance, threshold voltage and blocking characteristics after 80 hours HTRB reliability test at 200°C ambient. These promising experimental results indicate the possibility of the SiC stack-cascode for reliable 200°C operations.

Harsh environment applications such as electrical actuation on military and commercial aircraft, advanced engine controls, downhole energy exploration, propulsion systems of hybrid and all electric vehicles, and space exploration require sensor interfaces, control circuits, and power systems with electronics capable of operating at high temperatures. Wide band-gap materials such as SiC can be used to build devices with high operating temperatures due to their fundamental material properties. This paper presents initial results on developing basic analog and logic integrated circuits based on SiC JFET technology. Analog and logic integrated circuits were built using enhancement vertical channel lateral JFET transistors, metal film resistors and lateral p-n diodes. The analog circuits built include different types of operational amplifiers. The logic circuits include NOT, NAND, AND, NOR and OR gates. Transistors and integrated circuits were packaged in ceramic DIP packages and tested at temperatures up to 500 °C. The tested JFETs show proper operation up to the maximum tested temperature of 500 °C. The operational amplifiers remained functional at temperatures up to 430 °C. Basic logic circuits showed proper operation up to the maximum tested temperature of 500 °C.

A growing demand for smart and flexible photovoltaic power conversion and pulsed-power systems is leading to rapid development and commercialization of medium voltage 6.5 - 24 kV, wide-bang gap rectifiers and switches. Conventional silicon bipolar switches are limited to roughly 8 kV breakdown voltages and scaling up the voltage rating requires very thick wafers presenting significant manufacturing challenges. Very thick drift layers of silicon devices also translate into a very high minority carrier charge injected during forward conduction for an efficient conductivity modulation, hence leading to an extremely slow switching speed and poor efficiency. In this paper USCi presents the development of 6.5 kV 4H-SiC gate-turn-off thyristors (GTOs) with multiple floating guard-ring edge termination, and describes their application in an AC-link grid-tied solar inverter system.

There is a growing demand for medium voltage, 6.5-24 kV, switches capable of operating at more than 15 kHz frequencies. The range of potential applications includes grid-tied solar inverters and pulsed-power applications, where the conventional silicon thyristor technology is plagued with slow switching speeds at medium blocking voltage requirements. In this paper we present the design and characterization of 7.5 kV 4H-SiC Gate-Turn-Off thyristors (GTO's) with multiple floating guard-ring edge termination, and present GTO switching performance at 10 kHz in an AC-link™ [1] inverter.

The widespread adoption of energy storage deployment requires the cost for the power conversion stages to be significantly reduced. The high cost of inversion is driven largely by the performance limitations of Si-IGBTs and SiIGCTs, especially when a higher DC-link voltage (>1 kV) is desired to facilitate the reduction of the balance-of-system. SiC unipolar devices, however, offer great promise for increasing the DC link voltage, while maintaining high system efficiency without increasing system complexity. Such a switch platform could enable small, lightweight, transformerless topologies for industrial medium voltage grid applications operating at 3.3 or 4.16 kV AC. This report discusses the state-of-the-art 1.2kV SiC JFETs as a proven technology platform, and demonstrates the benefits of the JFET through operational comparisons with SiC-MOSFETs and Si-IGBTs. In addition, SiC JFET device reliability is demonstrated up to 200°C and the impact of a 6.5 kV JFET platform on power conversion systems is discussed.