High temperature characterization of SiC BJTs for power switching applications

SiC as a wide bandgap semiconductor material has attracted great interest in high power density and high temperature applications. Development of SiC-based power semiconductor devices has made remarkable progress and specific on-resistance ∼100 times lower than the best available silicon-based has been experimentally demonstrated [Zhao JH, Tone K, Li X, Alexandrov P, Fursin L, Weiner M. 3.6 m cm2, 1726 V 4H-SiC normally-off trenched-and-implanted vertical JFETs and circuit applications. IEE Proc – Circ, Dev Syst 2004;151(3):231–7]. However, progress in characterization and application of such devices in power electronics applications at a practically useful power level has so far been limited. In this paper, SiC BJTs with a blocking voltage of >1800 V are characterized in power switching applications for temperatures up to 275 °C. Inductive switching speeds under different load current and DC bus voltage conditions are studied. This is the first time a SiC switch has been characterized at a practically useful power level (300 V, 7 A) and a temperature substantially higher than any commercial power device is capable of. Current switching times of ∼10 ns have been demonstrated across the full temperature range. Switching speed of the SiC BJT has been found to remain virtually unchanged even at 275 °C. In addition, due to the lack of storage charge at even high temperature, switching storage time is negligible for the SiC BJT. The fast and stable switching speed of the SiC BJT at high temperature demonstrated in this paper makes the device an attractive candidate for high temperature, high frequency and high power density power electronics applications.