Noise parameter optimization of UHV/CVD SiGe HBT's for RF and microwave applications

This paper demonstrates a predictive noise parameter estimation methodology for UHV/CVD SiGe HBT's which combines ac measurement, calibrated ac simulation and two of the latest Y-parameter-based noise models: 1) the thermodynamic noise model, and 2) the SPICE noise model. The bias current and frequency dependence of the minimum noise figure, the optimum generator admittance, and the noise resistance are calculated using both models and compared with measurements. The observed agreements and discrepancies are investigated using circuit analysis of the chain noisy two-port representation. For the devices under study, the SPICE model description of thermal noise produces a better overall agreement to data in terms of all the noise parameters. Experiments on devices with different collector doping levels show that both low noise and high breakdown voltage ran be realized with one profile without significantly compromising the ac current gain and the ac power gain.