Low-Frequency Noise in Advanced SiGe:C HBTs-Part II: Correlation and Modeling

In part I, we extensively analyzed the results of the low-frequency noise characterization in advanced SiGe:C heterojunction bipolar transistors. In this paper, we demonstrate that base and collector noise spectral densities are partially correlated. The correlation is investigated by studying the coherence function at different bias conditions. The coherence reveals a frequency dependence at lower bias due to the presence of dominant generation-recombination mechanisms, whereas at higher bias, the coherence approaches unity. The bias dependence of the coherence is studied in several transistor geometries. In addition, a partially correlated base and collector 1/f noise model is proposed and implemented in HiCuM. Modeling results are in agreement with the measured data.