Jim Richmond

10-kV, 123-m/spl Omega//spl middot/cm/sup 2/ 4H-SiC power DMOSFETs

10-kV, 123-m/spl Omega//spl middot/cm/sup 2/ power DMOSFETs in 4H-SiC are demonstrated. A 42% reduction in R/sub on,sp/, compared to a previously reported value, was achieved by using an 8 /spl times/ 10/sup 14/ cm/sup -3/ doped, 85-/spl mu/m-thick drift epilayer. An effective channel mobility of 22 cm/sup 2//Vs was measured from a test MOSFET. A specific on-resistance of 123 m/spl Omega//spl middot/cm/sup 2/ were measured with a gate bias of 18 V, which corresponds to an E/sub ox/ of 3 MV/cm. A leakage current of 197 /spl mu/A was measured at a drain bias of 10 kV from a 4H-SiC DMOSFET with an active area of 4.24 /spl times/ 10/sup -3/ cm/sup 2/. A switching time of 100 ns was measured in 4.6-kV, 1.3-A switching measurements. This shows that the 4H-SiC power DMOSFETS are ideal for high-voltage, high-speed switching applications.

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.

Silicon carbide power MOSFETs: Breakthrough performance from 900 V up to 15 kV

Since Cree, Inc.s 2^nd generation 4H-SiC MOSFETs were commercially released with a specific on-resistance (R_{ON, SP}) of 5 mΩ·cm² for a 1200 V-rating in early 2013, we have further optimized the device design and fabrication processes as well as greatly expanded the voltage ratings from 900 V up to 15 kV for a much wider range of high-power, high-frequency, and high-voltage energy-conversion and transmission applications. Using these next-generation SiC MOSFETs, we have now achieved new breakthrough performance for voltage ratings from 900 V up to 15 kV with a R_{ON, SP} as low as 2.3 mΩ·cm² for a breakdown voltage (BV) of 1230 V and 900 V-rating, 2.7 mΩ·cm² for a BV of 1620 V and 1200 V-rating, 3.38 mΩ·cm² for a BV of 1830 V and 1700 V-rating, 10.6 mΩ·cm² for a BV of 4160 V and 3300 V-rating, 123 mΩ·cm² for a BV of 12 kV and 10 kV-rating, and 208 mΩ·cm² for a BV of 15.5 kV and 15 kV-rating. In addition, due to the lack of current tailing during the bipolar device switching turn-off, the SiC MOSFETs reported in this work exhibit incredibly high frequency switching performance over their silicon counter parts.

1000-V, 30-A 4H-SiC BJTs with high current gain

This paper presents the development of 1000 V, 30A bipolar junction transistor (BJT) with high dc current gain in 4H-SiC. BJT devices with an active area of 3/spl times/3 mm/sup 2/ showed a forward on-current of 30 A, which corresponds to a current density of 333 A/cm/sup 2/, at a forward voltage drop of 2 V. A common-emitter current gain of 40, along with a low specific on-resistance of 6.0m/spl Omega//spl middot/cm/sup 2/ was observed at room temperature. These results show significant improvement over state-of-the-art. High temperature current-voltage characteristics were also performed on the large-area bipolar junction transistor device. A collector current of 10A is observed at V/sub CE/=2 V and I/sub B/=600 mA at 225/spl deg/C. The on-resistance increases to 22.5 m/spl Omega//spl middot/cm/sup 2/ at higher temperatures, while the dc current gain decreases to 30 at 275/spl deg/C. A sharp avalanche behavior was observed at a collector voltage of 1000 V. Inductive switching measurements at room temperature with a power supply voltage of 500 V show fast switching with a turn-off time of about 60 ns and a turn-on time of 32 ns, which is a result of the low resistance in the base.

Roadmap for megawatt class power switch modules utilizing large area silicon carbide MOSFETs and JBS diodes

Recent dramatic advances in the development of large area Silicon Carbide (SiC) MOSFETs along with their companion JBS diode technology make it possible to design and fabricate high power SiC switch modules. An effort underway by the Air Force Research Laboratory has lead to the development of a 1.2kV/100A SiC dual switch power module capable of operating at a junction temperature of 200°C. Two additional efforts are set on achieving the megawatt goal. An effort by the Army Research Laboratory is focused on 1.2kV modules to be used for traction and power conversion applications. The highest power 1200V all-SiC dual switch power modules produced is capable of 880 amps. A DARPA effort to develop a solid state power substation has produced a 10kV/50A SiC dual switch power module. Higher current modules in both voltage ratings have been designed. These SiC MOSFET modules represent the next level of integration for SiC power devices. This is a critical technical milestone in the progression toward highly reliable, high efficiency, power systems. This technology is relevant in the current energy-conscious environment and will translate to significant energy savings for hybrid and electric vehicles, solar power and alternative energy system inverters, and industrial motor drives.

10 kV, 5A 4H-SiC Power DMOSFET

In this paper, we report 4H-SiC power DMOSFETs capable of blocking 10 kV. The devices were scaled up to 5 A, which is a factor of 25 increase in device area compared to the previously reported value. The devices utilized 100 mum thick n-type epilayers with a doping concentration of 6 times 1014 cm-3 for drift layers, and a floating guard ring based edge termination structure was used. The gate oxide layer was formed by thermal oxidation at 1175 degC, followed by an NO anneal. A peak effective channel mobility of 13 cm2/Vs was extracted from a test MOSFET with a W/L of 150 mum / 150 mum, built adjacent to the power DMOSFETs. A 4H-SiC DMOSFET with an active area of 0.15 cm showed a specific on-resistance of 111 mOmega-cm2 at room temperature with a gate bias of 15 V. The device shows a leakage current of 3.3 muA, which corresponds to a leakage current density of 11 muA-cm-2 at a drain bias of 10 kV

Comparison of Static and Switching Characteristics of 1200 V 4H-SiC BJT and 1200 V Si-IGBT

In this paper, static and switching characteristics of a 1200 V 4H-silicon carbide (SiC) bipolar junction transistor (BJT) at a bus voltage of 600 V are reported for the first time. Comparison was made between the SiC BJT and a 1200 V Si insulated gate bipolar transistor (IGBT). The experimental data show that the SiC BJT has much smaller conduction and switching losses than the Si IGBT. The SiC BJT also shows an extremely large reverse bias safe operation area, and no second breakdown was observed. This removes one of the most unattractive aspects of the BJT. The results prove that, unlike Si BJTs, BJTs in 4H-SiC are good competitors for Si IGBTs.

10 kV and 15 kV silicon carbide power MOSFETs for next-generation energy conversion and transmission systems

Advanced high-voltage (10 kV-15 kV) silicon carbide (SiC) power MOSFETs described in this paper have the potential to significantly impact the system performance, size, weight, high-temperature reliability, and cost of next-generation energy conversion and transmission systems. In this paper, we report our recently developed 10 kV/20 A SiC MOSFETs with a chip size of 8.1 × 8.1 mm2 and a specific on-resistance (RON, SP) of 100 MΩ-cm2 at 25 °C. We also developed 15 kV/10 A SiC power MOSFETs with a chip size of 8 × 8 mm2 and a RON, SP of 204 mQ cm2 at 25 °C. To our knowledge, this 15 kV SiC MOSFET is the highest voltage rated unipolar power switch. Compared to the commercial 6.5 kV Silicon (Si) IGBTs, these 10 kV and 15 kV SiC MOSFETs exhibit extremely low switching losses even when they are switched at 2-3× higher voltage. The benefits of using these 10 kV and 15 kV SiC MOSFETs include simplifying from multilevel to two-level topology and removing the need for time-interleaving by improving the switching frequency from a few hundred Hz for Si based systems to ≥ 10 kHz for hard-switched SiC based systems.

A 13 kV 4H-SiC n-Channel IGBT with Low Rdiff,on and Fast Switching

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.

An overview of Cree silicon carbide power devices

The compelling system benefits of using silicon carbide (SiC) Schottky diodes have resulted in rapid commercial adoption of this new technology by the power supply industry. Silicon carbide PiN diodes, MOSFETs, and BJTs, are approaching the point of development that they could be transitioned to volume production. This work reviews the characteristics of recently produced SiC devices including Schottky diodes, PiN diodes, MOSFETs, and BJTs. A comparison of the static and dynamic performance of the SiC devices and typical silicon devices is performed. The results show the performance improvement available with SiC devices. The high temperature performance capabilities of SiC devices are also highlighted.