Thermal effects on the dynamics of 4H-silicon carbide MOSFETs

Silicon carbide (SiC) devices are envisaged to play a major role in the development of integrated power systems and aircraft electric systems as required by the Department of Defense´s (DOD) More Electric initiative (MEI) and the More Electric Engines (MEE) program. The thermal effects on the static and dynamic characteristics of 4H-SiC UMOS devices fabricated by Cree, Inc., were investigated in the operating temperature range of 25°C to 200°C. The devices with a positive drain voltage of about 80 volts, were characterized in a high vacuum chamber to determine the effect of temperature on the on-resistance, threshold voltage and leakage current. The devices had a threshold voltage of 20 volts but the sub-threshold drain current was less than 500 μA. Dynamic thermal characterization was done to determine the effect of temperature on the switching time, switching losses, and reverse recovery. The rise, fall and turn-off delay times were 75 ns, 50 ns and 30 ns, respectively, with very low sensitivity to variation in temperature. The average power dissipation was 34 mW for the entire temperature range. Further testing is currently planned for high power devices to investigate the thermal effects on other dynamic characteristics