Noise in advanced bipolar transistors at mm-wave frequencies

Small-signal and noise characteristics of advanced InP/InGaAs, InGaP/GaAs and Si/SiGe heteroj unction bipolar transistors (HBTs) were measured and modeled over a broad frequency and collector current density range. HICUM was employed for modeling the HBTs and for analyzing them in terms of decomposed internal noise sources. Compared to Si/SiGe HBTs, higher noise is observed in InP/InGaAs HBTs, at lower frequencies due to the contribution of the higher base current and its related shot noise. The correlation between the collector current shot noise and the dynamic base current related shot noise in InP/InGaAs and Si/SiGe HBTs was found to be negligible in the 1-50 GHz frequency band in contrast to InGaP/GaAs HBTs. Although nonequilibrium electron transport was observed in InP and GaAs HBTs, the spectral density of intervalley scattering related current fluctuations has negligible impact on NF_min itself.