Broadband Noise Characterization of SiGe HBTs Down to 4K

This work presents a comprehensive noise characterization of advanced Si/SiGe:C Heterojunction Bipolar Transistors (HBTs) associated with a 0.13 µm BiCMOS technology. The study was carried out over a broad temperature spectrum (293 to 4 K) and a frequency range (10 kHz to 12 GHz). The noise characteristics of SiGe HBTs are inspected as functions of bias, frequency, and temperature; this is, to the best of our knowledge, the first study to cover these broad temperature and frequency ranges simultaneously. Through meticulous examination, we identify a substantial increase in the flicker noise coefficient KF, by a factor of 5.5 from 5.52×10-10 at 293 K to 3×10-9 at 4K. Furthermore, there is an increase in corner frequency for a constant collector current density Jc when the temperature is reduced to 4 K. Furthermore, to consider the enhancement of the high-frequency parameters (fT and fmax) reaching 500 GHz, related to this technology, we examined the ratio fc/fT, which connects the Low Frequency Noise (LFN) and the transistor speed. At 4 K, this ratio shows a minimum of 2×10-9 at 2mA/µm², which outperforms other advanced CMOS nodes. By addressing the modeling of HBTs that are the core active components of circuits used with quantum devices and sensors operating at deep cryogenic temperatures, we believe that this study will be beneficial to designers of classical-quantum interfaces in several emerging applications.