Robert Callanan

Recent progress in SiC DMOSFETs and JBS diodes at Cree

This paper discusses the recent progress in large area silicon carbide (SiC) DMOSFETs and junction barrier Schottky (JBS) diodes. 1.2 kV and 10 kV SiC DMOSFETs have been produced with die areas greater than 0.64 cm2. SiC JBS diode dies also rated at 1.2 kV and 10 kV have been produced with die areas exceeding 1.5 cm2. These results demonstrate that SiC power devices provide a significant leap forward in performance for industrial electronics applications. At 1.2 kV, SiC DMOSFETs offer a reduction of power loss of greater than 50 % with dies less than half the size when compared to silicon (Si) IGBTs. The SiC JBS diodes offer significant reductions in reverse recovery losses. At 10 kV, there are no Si devices that can compete with SiC on a single device basis. Data on 1.2 kV and 10 kV devices are presented along with future trends.

20 A, 1200 V 4H-SiC DMOSFETs for energy conversion systems

4H-SiC DMOSFETs designed to conduct up to 20 A and block in excess of 1200 V are described, and a performance comparison with comparably rated Si MOSFETs and IGBTs is presented. The 4H-SiC DMOSFETs show comparable to slightly improved on-state losses compared to the Si IGBTs and significantly improved performance over the Si MOSFET. Leakage currents of the 4H-SiC DMOSFETs are two orders of magnitude lower than those of the Si switches. Gate charge of the 4H-SiC DMOSFET is also reduced compared to the Si switches; moderately as compared to the Si IGBTs and quite significantly compared to the Si MOSFET, and total switching energy losses are 50% to 70% lower than those of the Si switches. The performance advantages in conduction and switching losses of the 4H-SiC DMOSFET permits operation to much higher frequencies and/or at higher junction temperatures than is achievable with the Si counterpart switches.

SiC power devices for Smart Grid systems

A Smart Grid with distributed generation is critical for reducing greenhouse gas emissions. However, current power converters and circuit breakers built with silicon switches are very bulky and inefficient, making their use difficult in practical Smart Grid systems. The development of high voltage power devices based on SiC will be a critical development in building a Smart Grid with distributed and fluctuating sources of power generation. In this paper, the physics and technology of high voltage (> 10kV) 4H-SiC power devices, namely MOSFETs, IGBTs, and GTOs, are discussed. A detailed review of the current status and trends in these devices is given with respect to materials growth, device design, and the potential future ranges for use.

State of the Art 10 kV NMOS Transistors

Rapidly improving 4 H-SiC material quality and a maturing MOS process/design have enabled the development of the largest 10 kV MOSFET to date and the first 10 kV n-IGBT capable of flowing 10 A and 4 A, respectively, with very low on- resistances. With 20 V on the gate, both devices have aVp~ 5V with a positive temperature coefficient for on-resistance that facilitates their use in a parallel configuration. Each device has its own advantages. The conductivity modulated n-IGBT offers higher current density operation (up to 100 A/cm ) while the majority carrier MOSFET offers extremely fast 5 kV switching with only 140 nsec of turn-off time and a manageable 160 W/cm of dissipated power at 20 kHz. These exciting results indicate that the 10 kV SiC NMOS switches may potentially revolutionize emerging high voltage, high frequency power electronics.

3.7 mΩ-cm 2 , 1500 V 4H-SiC DMOSFETs for advanced high power, high frequency applications

We present our most recent developments in 4H-SiC DMOSFETs. A 4H-SiC DMOSFET with an active area of 0.1 cm2 showed a specific on-resistance of 3.7 mΩ-cm2 with a gate bias of 20 V, and an avalanche voltage of 1500 V with gate shorted to source at 25°C. A threshold voltage of 3.5 V was extracted from the DMOSFET, and a subthreshold swing of 200 mV/dec was measured. The device was successfully scaled to an active area of 0.5 cm2, and the resulting device showed a drain current of 377 A at a forward voltage drop of 3.8 V at 25°C.

Design of 400V class inverter drive using SiC 6-in-1 power module

SiC devices are considered to be the next generation power device. This paper discusses thedesign of a Variable Frequency Drive (VFD) using a 6-in-1 power module that employs SiC-DMOSFETs and SiC Schottky Barrier Diodes (SBDs). A 400V class 11kW prototype drive is designed using a 1200V/50A SiC module by Cree. In this paper, power losses of SiC 6-in-1 module are measured and results are compared with an IGBT-based VFD. Analysis shows that SiC drive does not require current derating up to 60 kHz of PWM switching frequency while standard IGBT drive needs significant derating. High dv/dt and voltage reflection effects are important when fast switching devices like SiC are used. This paper explains the design of an optimal output filter.

Third quadrant behavior of SiC MOSFETs

This paper presents the third quadrant operating characteristics (VDS and ID both negative) of Crees SiC MOSFETs. This work includes information regarding the body diode characteristics, reverse I-V characteristics for various values of positive and negative gate bias, and the need for antiparallel diodes.

Status of 1200V 4H-SiC Power DMOSFETs

The commercial production of 1200 V 4H-SiC power MOSFETs is quickly becoming feasible in light of advances made in 4H-SiC substrate quality, improvements made in epitaxy, investigations of optimum device deign, advances made in increasing channel mobility with nitridation annealing, and optimization of device fabrication processes. These devices promise to enhance the efficiency of power handling circuits that currently rely on Si-based IGBTs. We routinely fabricate 1200 V power DMOSFETs with specific on-resistance (Ron(sp)) of 10 mOmega-cm² that show sub-microamps of leakage current at 1200 V with breakdown at greater than 1500 V. 1200V 4H-SiC DMOSFETs with active areas of 0.10 cm2 or 0.168 cm2 have been demonstrated for nominal current ratings of 10 A and 20 A, respectively.

1700V 4H-SiC MOSFETs and Schottky diodes for next generation power conversion applications

Junction barrier Schottky (JBS) diodes and MOSFETs fabricated in 4H-SiC are described. These power devices are capable of blocking in excess of 1700 V with leakage currents of less than tens of microamps at temperatures exceeding 175°C and of conducting tens of amps in the on-state. The static on-state and blocking I-V characteristics of each component are presented, along with a comparison to comparably rated Si bipolar PiN diodes and IGBTs. The dynamic performance of the 4H-SiC diodes and MOSFETs is also presented, and a fully functional 10 kW transformer isolated DC-DC power converter operating at 1000V at a switching frequency of 20 kHz is demonstrated.

3300 V, 30 A 4H-SiC power DMOSFETs

Wide band-gap SiC material provides power devices with superior electrical and thermal performance compared to Si power devices due to its higher electrical breakdown field and larger energy band-gap. 4H-SiC DMOSFETs have been attracting tremendous attentions for high-power applications owing to their normally-off characteristics, high speed switching operation, avalanche capability, and low on-resistance [1, 2]. In this work, we have demonstrated the 3300 V, 30 A 4H-SiC power DMOSFETs.