In this work, we report our recently developed 27 kV, 20 A 4H-SiC n-IGBTs. Blocking voltages exceeding 24 kV were achieved by utilizing thick (210 μm and 230 μm), lightly doped N-drift layers with an appropriate edge termination. Prior to the device fabrication, an ambipolar carrier lifetime of greater than 10 μs was measured on both drift regions by the microwave photoconductivity decay (μPCD) technique. The SiC n-IGBTs exhibit an on-state voltage of 11.8 V at a forward current of 20 A and a gate bias of 20 V at 25 °C. The devices have a chip size of 0.81 cm2and an active conducting area of 0.28 cm2. Double-pulse switching measurements carried out at up to 16 kV and 20 A demonstrate the robust operation of the device under hard-switched conditions; coupled thermal analysis indicates that the devices can operate at a forward current of up to 10 A in a hard-switched environment at a frequency of more than 3 kHz and a bus voltage of 14 kV.

Due to wider band gap of Silicon Carbide (SiC) compared to Silicon (Si), MOSFET made in SiC has considerably lower drift region resistance, which is a significant resistive component in high-voltage power devices. With low on-state resistance and its inherently low switching loss, SiC MOSFETs can offer much improved efficiency and compact size for the converter compared to those using Si devices. In this paper, we report switching performance of a new 1700V, 50A SiC MOSFET designed and developed by Cree, Inc. Hard-switching losses of the SiC MOSFETs with different circuit parameters and operating conditions are measured and compared with the 1700V Si BiMOSFET and 1700 Si IGBTs, using same test setup. Based on switching and conduction losses, the operating boundary of output power and switching frequency of each device are found out in a DC-DC boost converter and compared. The switching / and / of SiC MOSFET are captured and discussed in perspective of converter design. To validate the continuous operation, three DC-DC boost converters using these devices, are designed and tested at 10kW of power with 1kV of output voltage and 10kHz of switching frequency. 1700V SiC Schottky diode is used as the blocking diode in each case. Corresponding converter efficiencies are evaluated and the junction temperature of each device is estimated. To demonstrate high switching frequency operation, the SiC MOSFET is switched upto 150kHz within permissible junction temperature rise. A switch combination of the 1700V SiC MOSFET and 1700V SiC Schottky diode connected in series is also evaluated for zero voltage switching (ZVS) turn-ON behavior and compared with those of bipolar Si devices. Results show substantial power loss saving with the use of SiC MOSFET. Index Terms-1700V SiC MOSFET, 1700V Si IGBT, 1700V Si BiMOSFET, switching characterization, switching losses, converter efficiency, zero voltage switching (ZVS) turn-ON.

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Alkali (Rb and Cs) and alkaline earth (Ca, Sr, and Ba) elements have been investigated as interface passivation materials for metal-oxide-semiconductor field-effect transistors (MOSFETs) on 4H-SiC (0001). While the alkali elements Rb and Cs result in field-effect mobility (μFE) values > 25 cm2/V·s, the alkaline earth elements Sr and Ba resulted in higher μFE values of 40 and 85 cm2/V·s, respectively. The Ba-modified MOSFETs show a slight decrease in mobility with heating to 150 °C, as expected when mobility is not interface-trap-limited, but phonon-scattering-limited. With a Ba interface layer, the interface state density 0.25 eV below the conduction band is ∼3 × 1011 cm−2 eV−1, lower than that obtained with nitric oxide passivation. Devices show stable threshold voltage under 2 MV/cm gate bias stress at 175 °C, indicating no mobile ions. Secondary-ion mass spectrometry shows that the Sr and Ba stay predominantly at the interface after oxidation anneals.

Free electron concentration and carrier mobility measurements on 4H–SiC metal-oxide-semiconductor inversion layers are reported in this article. The key finding is that in state-of-the-art nitrided gate oxides, loss of carriers by trapping no longer plays a significant role in the current degradation under heavy inversion conditions. Rather, it is the low carrier mobility (maximum∼60 cm2 V−1 s−1) that limits the channel current. The measured free carrier concentration is modeled using the charge-sheet model and the mobility is modeled by existing mobility models. Possible mobility mechanisms have been discussed based on the modeling results.

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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 nextgeneration 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 mm 2 and a specific onresistance (R ON,SP ) of 100 mΩ⋅cm 2 at 25 °C. We also developed 15 kV/10 A SiC power MOSFETs with a chip size of 8 × 8 mm 2 and a R ON,SP of 204 mΩ⋅cm 2 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 2-3x higher voltage. The benefits of using these 10 kV and 15 kV SiC MOSFETs include simplifying from multilevel to twolevel 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.

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