Impacts of Finger Numbers on ON-State Characteristics in Multifinger SiC BJTs With Low Base Spreading Resistance

Impacts of finger numbers on ON-state characteristics in multifinger 10-kV-class SiC bipolar junction transistors (BJTs), whose base spreading resistance is sufficiently reduced by using aluminum ion implantation, were investigated by performing TCAD simulations. Common-emitter current-voltage characteristics of the BJTs with different base current densities and carrier lifetimes in the collector layer were analyzed. The simulation results exhibited that the BJTs with fewer finger numbers could achieve superior characteristics owing to an expansion of a conductivity-modulated region and to a higher current density per finger. In addition, we showed that BJTs with a punchthrough structure have a potential to achieve superior characteristics suitable for power device applications under a certain condition, where strong conductivity modulation occurs. The presented results indicate that the appropriate finger numbers should be designed for a better performance of the multifinger SiC BJTs.