Sige HBT performance and reliability trends through f_T of 350GHz

We discuss the SiGe HBT structural changes required for very high performance. The increase in collector concentration, affecting current density and avalanche current, appears to be the most fundamental concern for reliability. In device design, a narrow emitter and reduced poiy-single-crystal interfacial oxide are important elements in minimizing device parameter shifts. From the application point of view, avalanche hot-carriers appear to present new constraints, which may be managed through limiting voltage (to 1.5X-2X BVCEO), or through circuit designs robust to base current parameter shifts.