The dependence of the base current gain beta on the collector current I-C has been measured in high-voltage 4H-SiC bipolar junction transistors at collector current densities j(C) from 20 to 700 A/cm(2). With increasing collector current, the beta value grows, reaching a maximum beta(max) = 23 at j(C) of about 250 A/cm(2) and then decreasing sharply with further increase in current. The peculiarities of this dependence are analyzed in terms of a model taking into account the carrier recombination in the emitter space charge region (SCR), the surface recombination, and the emitter current crowding effect, It is shown that at relatively small j(C) the recombination in SCR plays a key role in limiting the beta magnitudes. The decrease in beta at high j(C) is mainly due to the surface recombination enhanced by the emitter current crowding effect. The effects of surface recombination and recombination in the SCR reduce the maximum current gain almost threefold: from 65 to 23. (C) 2002 Elsevier Science Ltd. All rights reserved.