Fabrication and Characterization of High-Current-Gain 4H-SiC Bipolar Junction Transistors

This paper reports on newly developed high-performance 4H-SiC bipolar junction transistors (BJT) with improved current gain and power handling capabilities based on an intentionally designed continuously grown 4H-SiC BJT wafer. The measured dc common-emitter current gain is as high as 70, the specific ON-state resistance (R_SP-ON) is as low as 3.0 mOmegamiddotcm², and the open-base breakdown voltage (V_CEO) reaches 1750 V. Large-area 4H-SiC BJTs with a footprint of 4.1 times 4.1 mm have been successfully packaged into a high-gain (beta = 50.8) high-power (80 A times 700 V) all-SiC copack and evaluated at high temperature up to 250degC. Small 4H-SiC BJTs have been stress tested under a continuous collector current density of 100 A/cm² for 24 h and, for the first time, have shown no obvious forward voltage drift and no current gain degradation. Numerical simulations and experimental results have confirmed that simultaneous high current gain and high open-base breakdown voltage could be achieved in 4H-SiC BJTs.