Main physical features of the collector resistance modulation processes have been studied via a one-dimensional simulation for n(+)-p-n(0)-n(+) 4H-SiC bipolar junction transistor. The motion dynamics of minority carriers (holes) across the n(0) collector layer during the switch-on process is traced. It is demonstrated that the effective modulation of the collector resistance is only possible in the case of a rather fast transistor switch-on. A necessary condition for the fast switch-on is the large amplitude and short leading edge of the base current pulse. (C) 2016 Elsevier Ltd. All rights reserved.