THE BASE COLLECTOR HETEROJUNCTION EFFECT IN SIGE BASE BIPOLAR-TRANSISTORS

This paper discusses a newly found advantage of Si/SiGe/Si heterostructure bipolar transistors (SiGe-base HBTs). We studied the base-collector heterojunction effect of the SiGe-base HBT using two-dimensional device simulation and circuit simulation, and found the following useful characteristics: First, the base-collector heterojunction has a two-order smaller carrier storage and a 0.3 V lower forward voltage drop, as compared with a silicon homojunction, so a high-speed and low-loss diode can be obtained. Second, the SiGe-base HBT shows little carrier accumulation even when operated in the saturation region, so it is expected to operate at high speed even in saturated mode switching. The SiGe-base HBT will provide highly efficient device elements for LSI circuits.