Two dimensional device modeling is used to investigate the differential DC current gain in 4H-SiC bipolar junction transistors using surface recombination velocity as one of the physical variables affecting the current gain. The simulated differential gain is compared with the measured experimental DC gain of transistors with two different emitter lengths. The comparison and the analysis made support the trend in modeling the DC gain as a function of surface recombination velocity and show that higher gain can be obtained for transistors with lower surface recombination velocity. (C) 2005 Elsevier Ltd. All rights reserved.