High-performance power BJTs in 4H-SiC

In this paper, we summarize recent progress in 4H-SiC BJTs at Purdue University. For 50 μm collector devices, BV_CEO>3,200 V is achieved. Large devices (active area=1.05 mm²) exhibit common emitter current gain β of around 15, and. specific on-resistance R_ON,SP of 78 mΩ/cm². Smaller devices (active area=0.0072 mm²) have β of 20 and R_ON,SP of 28 mΩ/cm². For 20 μm collector devices, βs greater than 50 and R_ON,SP around 26 mΩ/cm² are observed. The blocking voltage is low (500-700 V) for these devices because of aluminum spiking during the base contact anneal. The observed positive temperature coefficient of R_ON,SP and negative coefficient of β show that 4H-SiC BJTs can be safely operated in parallel connection. We also observe that β decreases as the spacing between base contact implant and emitter finger is reduced. We attribute this to recombination at defect sites in the p+ implanted base contact.