High frequency performance of SiC heterojunction bipolar transistors

A compact heterojunction bipolar transistor (HBT) model was employed to simulate the high frequency and high power performances of SiC-based bipolar transistors. Potential 6H-SiC/3C-SiC heterojunction bipolar transistors (6H/3C-HBT´s) at case temperatures of 27°C (300 K) through 600°C (873 K) were investigated. The high frequency and high power performance was compared to AlGaAs/GaAs HBT´s. As expected, the ohmic contact resistance limits the high frequency performance of the SiC HBT. At the present time, it is only possible to reliably produce 1×10^-4 Ω-cm² contact resistances on SiC, so an f_T of 4.4 GHz and an f_max of 3.2 GHz are the highest realistic values. However, assuming an incredibly low 1×10^-6 Ω-cm² contact resistance for the emitter, base, and collector terminals, an f_T of 31.1 GHz and an f_max of 12.7 GHz can be obtained for a 6H/3C-SiC HBT