Silicon Carbide Junction Barrier Schottky Diodes Research Articles

Unveiling microstructural damage for leakage current degradation in SiC Schottky diode after heavy ions irradiation under 200 V

Single-event burnout and single-event leakage current (SELC) in silicon carbide (SiC) power devices induced by heavy ions severely limit their space application, and the underlying mechanism is still unclear. One fundamental problem is lack of high-resolution characterization of radiation damage in the irradiated SiC power devices, which is a crucial indicator of the related mechanism. In this Letter, high-resolution transmission electron microscopy (TEM) was used to characterize the radiation damage in the 1437.6 MeV 181Ta-irradiated SiC junction barrier Schottky diode under 200 V. The amorphous radiation damage with about 52 nm in diameter and 121 nm in length at the Schottky metal (Ti)–semiconductor (SiC) interface was observed. More importantly, in the damage site the atomic mixing of Ti, Si, and C was identified by electron energy loss spectroscopy and high-angle annular dark-field scanning TEM. It indicates that the melting of the Ti–SiC interface induced by localized Joule's heating is responsible for the amorphization and the possible formation of titanium silicide, titanium carbide, or ternary phases. The mushroom-like hillock in the Ti layer can be attributed to Rayleigh–Taylor instability, as another evidence for ever-happened localized melting near the Schottky interface. These modifications at nanoscale in turn cause localized degradation of the Schottky contact, resulting in permanent increase in leakage current. This experimental study provides very valuable clues for a thorough understanding of the SELC mechanism in SiC diodes.

Chip packaging interaction of SiC junction barrier Schottky diode packages

Wide band gap semiconductors are attractive in the electric vehicle industry because of their higher operating temperatures, and lower switching losses than those of silicon semiconductors. However, the electric vehicle industry has driven the development of more reliable semiconductors because of safety issues. Among several reliability issues, the reliability at the chip level can be a challenging problem because chip-related failures are difficult to observe in the early design stage. In this study, the chip package interaction for a silicon carbide (SiC) junction barrier Schottky diode package was investigated to estimate the stresses of the chip layers at the package level. This methodology will help power semiconductor manufacturers perform a robust design of their packages in terms of SiC chip reliability. Moreover, the response surface methodology can be used to establish a correlation between the maximum stresses of the passivation layer and three-wire bonding conditions. This methodology can be used to determine optimal wire-bonding conditions to improve chip reliability.

A SiC-Si Hybrid Module for Direct Matrix Converter With Mitigated Current Spikes

Reliable and affordable ac/ac power conversion plays a key role in supplying various electrical equipment. Among the options available, the direct matrix converter (DMC) outperforms its counterparts (e.g., ac/dc/ac), in terms of lifespan and compactness, due to its omission of fragile and bulky dc-link capacitors. However, most off-the-shelf DMC modules suffer from high input current spikes, which if unresolved can noticeably increase current stresses and lower efficiency. Origin of the spikes and a mechanism for reducing them are hence studied in this article, before developing a low-cost silicon carbide (SiC)-Si hybrid module for implementing DMC reliably and compactly. The developed module consists of 18 Si insulated gate bipolar transistors (IGBTs) and 18 SiC junction barrier Schottky (JBS) diodes connected in a common-collector structure. The improved reverse recovery property of the SiC JBS diodes then permits the hybrid module to operate with mitigated current spikes. To demonstrate, the hybrid module has been fabricated, tested, and compared with two counterparts in terms of their input current spikes and power losses over different output voltages and switching frequencies. Experimental results have proved the expected performances of the hybrid DMC module, which collectively can accelerate large-scale emergence of small all-semiconductor drives for industrial pumps, cooling and refrigeration systems, and others widely needed in developing economies.

Design, Package, and Hardware Verification of a High-Voltage Current Switch

This paper demonstrates various electrical and package design considerations in series connecting a high-voltage (HV) silicon (Si)-IGBT (6500-V/25-A die) and a silicon carbide-junction barrier Schottky diode (6500-V/25-A die) to form an HV current switch. The effects of connecting the cathode of the series diode to an IGBT collector, versus connecting the IGBT emitter to the anode of the series diode, are analyzed in regards to minimizing the parasitic inductance. An optimized package structure is discussed and an HV current switch module is custom fabricated in the laboratory. An HV double pulse test circuit is used to verify the switching performance of the current switch module. Low-voltage and HV converter prototypes are developed and tested to ensure thermal stability of the same. The main motivation of this paper is to enumerate detailed design considerations for packaging an HV current switch.

Modeling of the High-Frequency Rectifier With 10-kV SiC JBS Diodes in High-Voltage Series Resonant Type DC–DC Converters

The superior material properties of the wide bandgap silicon carbide (SiC) semiconductors enable excellent device characteristics such as low on-resistance, high breakdown voltage, fast switching speed, high temperature operation, etc. 10-kV SiC junction barrier Schottky (JBS) diode prototype made by Cree was characterized in this paper first. The high-voltage (HV) and high-frequency rectifier consisting of SiC JBS diodes in dc-dc converters can potentially benefit from the device characteristics. However, capacitive current in both forward and reverse recovery process is observed due to the junction capacitance when the SiC JBS diode is turned on and off, which increases the reactive power and reduces the rectifier output power and voltage. To better utilize the devices, the rectifier operation is analyzed in consideration of the impact of the JBS diode parasitic capacitance. Two equivalent circuit models, the series and the parallel input impedance model, are proposed. The distributed junction capacitance of JBS diodes is lumped into the equivalent input capacitance such that the input impedance and output voltage, two critical parameters in HV dc-dc converter design, can be predicted from the models. Experiment setup of SiC JBS diode rectifier was built and the test results verified the modeling work.

Evaluation of a 1200-V, 800-A All-SiC Dual Module

Enhanced material properties of silicon carbide (SiC) offer improved performance capabilities for power electronic devices compared to traditional silicon (Si) components. This paper reports on the experimental characterization of a 1200-V, 800-A all-SiC dual power module that incorporates twenty 80-A SiC MOSFETs and twenty 50-A SiC junction barrier Schottky diodes. Forward and reverse conduction characteristics were measured at multiple gate voltages, current sharing was examined between the MOSFETs, and switching energies were calculated for various currents. Additionally, this module has operated in a full-bridge circuit with a peak loading of 900 A <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dc</sub> , a 600 V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dc</sub> bus, and a junction temperatures of 153°C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">.</sub> From the experimental data, a model of the module was created and used in a dc-ac inverter simulation study to demonstrate the possible benefits of SiC compared to Si technology. The use of an all-SiC module was shown to reduce inverter losses by 40% or more for most operating conditions. Furthermore, for similar output current levels, the all-SiC module can operate at switching frequencies four times higher than that of the Si module. This advanced dual power module demonstrates the ability to produce a high-current high-power switch using SiC technology.

Development of a 15 kV bridge rectifier module using 4H-SiC junction-barrier schottky diodes

To demonstrate higher efficiency and more compact high-voltage power conversion systems, a 15 kV full-bridge rectifier module has been developed by the U.S. Army Research Laboratory. The module utilizes 15 kV, 3 A silicon carbide junction-barrier Schottky diodes manufactured by CREE Inc. In this paper, we will present the analyses, design, and characterization of this module using conventional materials and processes and introduce a novel technique to reduce electric field stress and associated failure modes.