This paper presents the third quadrant operating characteristics (V-DS and I-D both negative) of Cree's 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.

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.

We present our recent developments in 4H-SiC power DMOSFETs. 4H-SiC DMOSFETs with a room temperature specific on-resistance of 3.7 mΩ-cm2 with a gate bias of 20 V, and an avalanche voltage of 1550 V with gate shorted to source, was demonstrated. A threshold voltage of 3.5 V was extracted from the power DMOSFET, and a subthreshold swing of 200 mV/dec was measured. The device was successfully scaled to an active area of 0.4 cm2, and the resulting device showed a drain current of 377 A at a forward voltage drop of 3.8 V at 25oC.

Silicon carbide (SiC) materials technology has made rapid advances in recent years. While increasing the wafer diameter from 75 mm to 100 mm, the substrate quality has been greatly improved with much reduced defect density, resulting in higher device yields. Cree is poised to increase the wafer diameter to 150 mm in 2012, which will further reduce the cost of SiC devices. SiC Schottky diodes have demonstrated very high reliability in the field and are being extensively used in Switch Mode Power Supplies (SMPS), and solar inverters, and other applications. Cree has also commercially released a 1200 V, 20 A SiC MOSFET which has been used in solar inverter along with SiC Schottky diode to provide an efficiency gain of 2.36%. More recent R&D results at Cree indicate that the on-resistance of the MOSFET can be reduced by 2x, which will further improve performance and reduce cost.

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.

DMOSFETs fabricated in 4H-SiC with capabilities for blocking in excess of 1700V and conducting 20A continuous current in the on-state are presented. These SiC DMOSFETs remain functional to temperatures in excess of 225°C, with leakage current at 1700V at 225°C of less than 5 A with VGS = 0V. The DMOSFETs show excellent switching characteristics, with total switching energy of 1.8 to 1.95 mJ over the entire temperature range of testing (25°C to 200°C), when switched from the blocking state at 1200V to conducting at 20A in a clamped inductive load switching circuit. The electrical characteristics are compared to commercially available Si IGBTs rated to 1700V with similar current ratings as the SiC DMOSFET described herein.

We present our most recent developments in 4H-SiC DMOSFETs. A 4H-SiC DMOSFET with an active area of 0.1 cm 2 showed a specific on-resistance of 3.7 mΩ-cm 2 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 cm 2 , and the resulting device showed a drain current of 377 A at a forward voltage drop of 3.8 V at 25°C.

In this paper, for the first time, we report a large area (1 cm2) SiC GTO with 9 kV blocking voltage fabricated on 100-mm 4H-SiC substrates with much reduced Basal Plane Dislocation (BPD) density. The static and dynamic characteristics are described. A forward drop of 3.7 V at 100 A (100 A/cm2) is measured at 25°C. A slight positive temperature coefficient of the forward drop is present at 300 A/cm2, indicating the possibility of paralleling multiple devices for higher current capability. The device exhibits extremely low leakage currents at high temperatures. The device has shown fast turn-on time of 53.9 nsec, and ~3.5 s of turn-off time, respectively. A stable forward voltage drop after electrical stress for >1000 hours has been achieved.

In this paper, for the first time, we report a large area (1 cm(2)) SiC GTO with 9 kV blocking voltage fabricated on 100-mm 4H-SiC substrates with much reduced Basal Plane Dislocation (BPD) density. The static and dynamic characteristics are described. A forward drop of 3.7 V at 100 A (100 A/cm(2)) is measured at 25 degrees C. A slight positive temperature coefficient of the forward drop is present at 300 A/cm(2), indicating the possibility of paralleling multiple devices for higher current capability. The device exhibits extremely low leakage currents at high temperatures. The device has shown fast turn-on time of 53.9 nsec, and similar to 3.5 mu s of turn-off time, respectively. A stable forward voltage drop after electrical stress for >1000 hours has been achieved.

4H-SiC Bipolar Junction Transistors (BJTs) and hybrid Darlington Transistors with 10 kV/10 A capability have been demonstrated for the first time. The SiC BJT (chip size: 0.75 cm2 with an active area of 0.336 cm2) conducts a collector current of 10 A (~ 30 A/cm2) with a forward voltage drop of 4.0 V (forced current gain βforced: 20) corresponding to a specific on-resistance of ~ 130 mΩ•cm2 at 25°C. The DC current gain, β, at a collector voltage of 15 V is measured to be 28 at a base current of 1 A. Both open emitter breakdown voltage (BVCBO) and open base breakdown voltage (BVCEO) of ~10 kV have been achieved. The 10 kV SiC Darlington transistor pair consists of a 10 A SiC BJT as the output device and a 1 A SiC BJT as the driver. The forward voltage drop of 4.5 V is measured at 10 A of collector current. The DC forced current gain at the collector voltage of 5.0 V was measured to be 440 at room temperature.

La presente invention concerne un dispositif electronique qui comprend un thyristor a large bande interdite comportant une anode, une cathode et une borne de grille, ainsi qu'un transistor bipolaire a large bande interdite comportant une base, un collecteur et une borne d'emetteur. La borne d'emetteur du transistor bipolaire est directement couplee a la borne d'anode du thyristor de sorte que le transistor bipolaire et le thyristor soient raccordes en serie. Le transistor bipolaire et le thyristor definissent un dispositif de commutation de puissance bipolaire a large bande concu pour commuter entre un etat non conducteur et un etat conducteur qui permet au courant de circuler entre une premiere borne principale correspondant a la borne du collecteur du transistor bipolaire et une seconde borne principale correspondant a la borne de cathode du thyristor en reponse a l'application d'un premier signal de commande a la borne de base du transistor bipolaire et en reponse a l'application d'un second signal de commande a la borne de grille du thyristor. L'invention concerne egalement des circuits de commande associes.

Microgrids with distributed generation sources are critical for reduction of greenhouse gas emissions and imported energy. However, power converters and circuit breakers built with silicon (Si) switches are too bulky and inefficient to be used in the microgrid system. The development of high-voltage power devices based on silicon carbide (SiC) will be a critical component in building the microgrid with distributed and fluctuating sources of power generation. In this paper, the physics and technology of high-voltage (>10 kV) 4H-SiC power devices, namely MOSFETs and insulated gate bipolar transistors are discussed. A detailed review of the current status and future trends in these devices is given with respect to materials growth, device design, and fabrication processing.

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 (> 10 kV) 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.

Silicon Carbide (SiC) is an extremely attractive material for semiconductor power devices because of its electrical and physical characteristics. This paper describes the benefits of utilizing SiC Super Gate Turn-Off thyristors (SGTO) in pulsed power applications, reviews the current progress and development of SiC GTOs, and presents the static and pulsed characteristics of large area GTOs with high blocking capabilities. The wide pulsed evaluation of the 0.5cm2 SiC SGTOs has been demonstrated and reported by the Army Research Laboratory (ARL). This paper presents the wide pulsed capabilities of the 1cm2 SiC SGTOs. The 1cm2 SiC SGTO devices handled up to twice the peak current of the 0.5cm2 SiC SGTOs at a 1ms pulse width. The wide pulsed evaluation of these devices was demonstrated at ARL. ARL evaluated the static and pulsed characteristics of six of these devices. The devices had a forward blocking voltage rating of 9kV and a trigger requirement of a negative pulse of 1A to the gate for a millisecond pulse width. These devices were pulsed as high as 3.5kA at 1ms, equating to an action rate of 6×103A2s and a current density of 4.8kA/cm2, based on the device active area. The narrow pulsed evaluation of this device has been demonstrated by Cree Inc. A peak current of 12.8kA with a pulse width of 17μs (corresponding to 12.8kA/cm2 based on the chip size) was conducted with this device.

For the first time, high power 4H-SiC n-IGBTs have been demonstrated with 13 kV blocking and a low Rdiff,on of 22 mWcm2 which surpasses the 4H-SiC material limit for unipolar devices. Normally-off operation and >10 kV blocking is maintained up to 200oC base plate temperature. The on-state resistance has a slight positive temperature coefficient which makes the n-IGBT attractive for parallel configurations. MOS characterization reveals a low net positive fixed charge density in the oxide and a low interface trap density near the conduction band which produces a 3 V threshold and a peak channel mobility of 18 cm2/Vs in the lateral MOSFET test structure. Finally, encouraging device yields of 64% in the on-state and 27% in the blocking indicate that the 4H-SiC n-IGBT may eventually become a viable power device technology.

In this paper, for the first time, large area SiC BJTs were fabricated on SiC wafers with reduced Basal Plane Dislocations (BPDs). We have demonstrated: (1) stable performance on 1200 V, 20 A SiC BJTs after long duration of electrical stress at different current densities up to 150 A/cm2; (2) a blocking yield of >80% with low leakage current (<20 nA at 1800 V) on 3" wafers along with current gains in a range of 35-40. Both breakthroughs highlight the possibility for SiC BJTs to be commercialized and utilized in power electronics.