Sic Dmosfet Characterization And Evaluation For Power Electronics Applications
MetadataShow full item record
Type of WorkText
DepartmentElectrical and Computer Engineering
ProgramDoctor of Engineering
RightsThis item is made available by Morgan State University for personal, educational, and research purposes in accordance with Title 17 of the U.S. Copyright Law. Other uses may require permission from the copyright owner.
As SiC MOSFET technology continues to mature, an assessment of device reliability becomes essential for the development of large power modules utilizing this technology. This dissertation investigated state-of-the-art 4H-SiC DMOSFETs for continuous power electronics applications. The research methodology consisted of performing a variety of electrical measurements that characterized device performance, and studied device stability and reliability. A 400-A power module utilizing SiC MOSFET technology was fabricated, tested and implemented in a continuous power conversion application circuit. The module features an integrated heat sink design and form factor that is compliant to commercial IGBT modules with similar rating. Switch-mode testing of the module in a power converter circuit demonstrated operation at 25 kW and 30 kHz switching frequency with an ambient temperature of 80 °C. On-state performance of 1200 V class SiC MOSFET devices is currently limited by charge trapping at the SiC-SiO2 interface. As a result, the channel mobility is very low (μch ≈ 20 cm2/V∙s) and the total specific on-resistance (Ron-sp) is dominated by the channel resistance. The temperature dependence of Ron-sp was shown to be a function of the applied gate voltage. Two separate scattering mechanisms are responsible for the difference in the temperature response of Ron-sp that occurs at low and high gate voltages. The threshold voltage (VT) of these devices has strong temperature dependence which can limit the blocking performance. Subthreshold leakage current through the MOS channel increases with increasing temperature due to the shift in VT. This results in a higher drain leakage current during the off-state as the device temperature is raised. Device reliability may be impacted if VT is not set high enough to preclude subthreshold leakage current during off-state operation. It has been demonstrated that application of a negative gate bias can suppress this leakage current and enhance off-state performance. Switching performance of 4H-SiC MOSFET devices was characterized as a function of temperature in a double-pulse clamped inductive load test circuit. The total switching energy loss was found to decrease with increasing temperature due to the shift in VT. Modified High Temperature Gate Bias (MHTGB) and High Temperature Reverse Bias (HTRB) measurements on SiC MOSFET devices have achieved stress times of 100 and 50 hours respectively, with no failures. This work provides a first look at the long-term reliability of these devices.