We evaluate the performance capabilities and limitations of high voltage 4H-SiC based
Bipolar Junction Transistors (BJTs). Experimental forward characteristics of a 4kV BJT are studied
and simulations are employed to determine the factors behind the higher than expected specific onresistance
(Ron,sp) for the device. The impact of material (minority carrier lifetimes), processing
(surface recombination velocity) and design (p contact spacing from the emitter mesa) parameters
on the forward active performance of this device are discussed and ways to lower Ron,sp, below the
unipolar level, and increase the gain (β) are examined.