SiGe HBT Technology for High Speed Integrated Circuits

The graded-SiGe-base heterojunction bipolar transistor (SiGe HBT) offers three main advantages over conventional silicon bipolar junction transistors [1]: 1 ) a quasi-electric drift field in the base that reduces base transit time, leading to higher frequency performance; 2) a band offset at the emitter-base junction that lowers the potential barrier to electron injection into the base, exponentially increasing collector current; and 3) bandgap grading across the base that exponentially increases the Early voltage.