Bejoy N. Pushpakaran

GaN Technology for Power Electronic Applications: A Review

Power semiconductor devices based on silicon (Si) are quickly approaching their limits, set by fundamental material properties. In order to address these limitations, new materials for use in devices must be investigated. Wide bandgap materials, such as silicon carbide (SiC) and gallium nitride (GaN) have suitable properties for power electronic applications; however, fabrication of practical devices from these materials may be challenging. SiC technology has matured to point of commercialized devices, whereas GaN requires further research to realize full material potential. This review covers fundamental material properties of GaN as they relate to Si and SiC. This is followed by a discussion of the contemporary issues involved with bulk GaN substrates and their fabrication and a brief overview of how devices are fabricated, both on native GaN substrate material and non-native substrate material. An overview of current device structures, which are being analyzed for use in power switching applications, is then provided; both vertical and lateral device structures are considered. Finally, a brief discussion of prototypes currently employing GaN devices is given.

Failure Analysis of 1200-V/150-A SiC MOSFET Under Repetitive Pulsed Overcurrent Conditions

SiC MOSFETs are a leading option for increasing the power density of power electronics; however, for these devices to supersede the Si insulated-gate bipolar transistor, their characteristics have to be further understood. Two SiC vertically oriented planar gate D-MOSFETs rated for 1200 V/150 A were repetitively subjected to pulsed overcurrent conditions to evaluate their failure mode due to this common source of electrical stress. This research supplements recent work that demonstrated the long term reliability of these same devices [1]. Using an RLC pulse-ring-down test bed, these devices hard-switched 600 A peak current pulses, corresponding to a current density of 1500 A/cm2. Throughout testing, static characteristics of the devices such as BVDSS, RDS (on), and VGS(th) were measured with a high power device analyzer. The experimental results indicated that a conductive path was formed through the gate oxide; TCAD simulations revealed localized heating at the SiC/SiO2 interface as a result of the extreme high current density present in the devices JFET region. However, the high peak currents and repetition rates required to produce the conductive path through the gate oxide demonstrate the robustness of SiC MOSFETs under the pulsed overcurrent conditions common in power electronic applications.

High Temperature Unclamped Inductive Switching Mode Evaluation of SiC JFET

Silicon carbide (SiC) unipolar transistors are an efficient choice in the design of high temperature 1200 V switching power supplies and dc-dc converters. To reduce the form factor and increase the power density of the circuit, the switching frequency must be high. This intensifies the negative impact of parasitic inductance and results in high voltage spikes that can drive a switching device into breakdown, followed by rapid destruction. To study the device performance under unclamped inductive switching (UIS) conditions, a normally-ON 1200 V/13-A SiC junction field-effect transistor (JFET) is driven into punch through breakdown using a single pulse. The testing is performed using an UIS setup, in which energy initially stored in an inductor is discharged through the JFET. The testing comprises of 90 single pulses each at 25°C and 100 °C case temperatures for different gate voltages and drain current values. The peak energy and power dissipated in the JFET are 621 mJ and 16 kW, respectively, at the rated 1200 V blocking voltage and 13-A drain current. The JFET triode breakdown characteristics are unchanged after 180 single-pulse switching events indicating the robust nature of the device under extreme breakdown conditions. In addition, the 621 mJ peak UIS energy and its corresponding 8871 mJ/cm2 density dissipated in the JFET are the highest reported for any SiC power device.

Electro-thermal transient simulation of silicon carbide power MOSFET

This research illustrates the transient performance of N-channel silicon carbide (4H-SiC) power MOSFET rated for a blocking voltage of 1200V and drain current density of 100A/cm2. The simulation of vertical D-MOSFET half cell structure was performed at room temperature of 300K. The 2D device model was created and simulated using Silvaco© ATLAS Technology Computer-Aided Design (TCAD) physics based simulation software. Physics based models were used to accurately model electrical device parameters including carrier mobility, recombination effects, bandgap narrowing, impact ionization and lattice heating.

Silicon Carbide Technology Overview

Silicon Carbide Technology Overview nAfter several years of research and development, Silicon Carbide has emerged as a prominent successor to conventional silicon in the field of power electronics due to its exceptional advantages. Silicon carbide material improves the efficiency of semiconductor devices and also facilitates usage of devices with much smaller form factor. The chemical and electronic properties of Silicon carbide translate to features which are useful for semiconductors especially in high power applications. These features include inherent radiation-resistance, high-temperature operating capacity, high voltage and power handling capacity. The use of SiC specifically in the areas of industrial control, power and renewable energy (solar & wind sector) also enables smaller cooling solutions in the system design. SiC electronics also find applications in electric vehicles and hybrid electric vehicles, electric traction control, power supply units, photovoltaic applications, converters and inverters.

Fast and accurate electro-thermal behavioral model of a commercial SiC 1200V, 80 mΩ power MOSFET

The superior electro-thermal properties of Silicon Carbide (SiC) as compared to silicon make them a viable candidate for high voltage and high frequency applications. Due to the relatively recent surge in commercially available SiC power MOSFETs, there is an immediate demand for accurate simulations models to predict device behavior and aid circuit design process. This paper discusses the development of an accurate SPICE based model for a commercially available 1200V, 20A SiC power MOSFET manufactured by CREE Inc. based on the Enz - Krummenacher - Vittoz (EKV) MOSFET model. The advantage of using EKV model over the simplified quadratic model is the ability to characterize MOSFET behavior over weak, moderate and strong inversion regions with a single equation. The model was developed using parameters extracted through experimental data conducted at wide temperature range. Package parasitic components have been incorporated into the model to predict device behavior in high frequency switching applications. The model was simulated for its static and transient behavior and compared with actual device results to determine accuracy over a wide operating range.

Single-Pulse Avalanche Mode Robustness of Commercial 1200 V/80 mΩ SiC MOSFETs

Commercialization of 1200-V silicon carbide (SiC) MOSFET has enabled power electronic design with improved efficiency as well as increased power density. High-voltage spikes induced in applications such as solenoid control, solid-state transformer, boost converter, and flyback converter can drive the MOSFET into avalanche mode operation due to high <italic>di</italic>/<italic>dt</italic> coupled with parasitic inductance. Avalanche mode operation is characterized by high-power dissipation within the device due to the high voltage and current crossover. This study focuses on the evaluation of two commercially available SiC MOSFETs from different manufacturers, each rated for 1200 V with an ON-state resistance of 80 mΩ, during unclamped inductive switching (UIS) mode operation. To determine device reliability, a decoupled UIS testbed was developed to evaluate the avalanche energy robustness at 22 <inline-formula><tex-math notation=LaTeX>

Evaluation of SiC JFET Performance During Repetitive Pulsed Switching Into an Unclamped Inductive Load

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Physics based electro-thermal transient simulation of 4H-SiC JBS diode using Silvaco ATLAS

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Analysis of carrier lifetime effects on HV SIC PiN diodes at elevated pulsed switching conditions

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