Device simulations of B implanted 4H-SiC p(+)nn(+) diodes were performed including transient trapping of carriers in the deep B level. Most traps become filled at forward current densities above 3000 A/cm(2) thus enabling conductivity modulation by a carrier plasma and a negative resistance in agreement with pulsed forward bias measurements. Reverse recovery measurements were performed to verify a significant conductivity modulation at 4000 A/cm(2) and the absence of this at 1000 A/cm(2) in agreement with simulations.