The effect of the different types of passivation layers on the current gain of SiC BJTs has been investigated. Measurements have been compared for BJTs passivated with thermal SiO2, plasma deposited (PECVD) SiO2 and BJTs without passivation. The maximum DC current gain of BJTs with thermal SiO2 was about 62 at IC=20 mA and Vce=40 V. On the other hand, the BJTs with a passivation by PECVD SiO2 had a DC current gain of only 25. The surface recombination current was extracted from measurements with BJTs of different emitter widths. The surface recombination current of BJTs with a thermally grown oxide was about 25 % lower than unpassivated BJTs and 65 % lower than that of PECVD passivated BJTs.