Electrical stress effect on RF power characteristics of SiGe hetero-junction bipolar transistors

In this paper, we investigate the electrical stress effects on both the high-frequency and RF power characteristics of Si/SiGe HBTs. Simultaneously applying a high collector current density and a high collector–base voltage upon the Si/SiGe HBTs, their hot carriers will induce device performance degradation. This stress condition is similar to the DC bias conditions of a current source RF power amplifier, and is termed as a “mixed-mode” stress. We find that not only the maximum oscillation frequency but also the output power performance of Si/SiGe HBTs are suffered by this electrical stress. In addition, the degradations of high-frequency and power characteristics are also worse under a constant base-current measurement than those under a constant collector-current measurement. Finally, we developed a commercial large-signal model to examine the degradations of the parasitic resistances and ideality factors of base and collector currents to explain the RF power and linearity degradations.