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|1200V 20A SiC BJTs Operating at 250C|
|Keywords: SiC, power, transistor|
|Silicon carbide (SiC) bipolar junction transistors (BJTs) are normally-off devices blocking high voltages at high tem-perature operation . Conduction losses are low and switching times are very short resulting in very low losses  compared to silicon (Si) power transistors. SiC BJTs are also very tolerant to radiation and are inherently robust devices. The RBSOA is wide and provide good short circuit capabilities . It is possible to get low saturation voltage without the driving the transistor into deep saturation giving the fast switching capabilities. All these good properties come from the high critical field strength of SiC. Vertical 1200V 20A NPN SiC BJTs rated at 250 ˚C with a schematic cross-section shown in Figure 1 were fabricated. The BJT's were packaged in a high-temperature capable metal package of the type TO-258 (see Figure 2), capable of operating at 250˚C. A SPICE model has been developed for the SiC BJT to accurately describe important parameters such as current gain, collector series resistance as well as the base-collector and base-emitter capacitances, as a function of operating temperature. The high temperature characteristics of the model and experimental measurements are correlated up to 250˚C, to show the accuracy of the developed model (see Figure 3). The transistors can operate well above 250˚C but the measurements are limited up to this temperature by the packaging. One of the target applications for these transistors is switched power for harsh environments, such as DC/DC conver-ters, DC/AC inverters and motor drives. An important factor when designing switched power is the switching behavior of the power devices. This makes it important that the model accurately describes the switching characteristics as well. Simulated high temperature switching will be compared to real measurements. The robustness of the transistors is also a very important aspect short circuit testing will be done and presented at high temperatures.|
|Anders Lindgren, Application Engineer