The accuracy of the SPICE and unified compact noise models is assessed in the RF range by comparison with the hydrodynamic device model for a state-of-the-art SiGe HBT with a low base resistance. Despite the low base resistance, as a general result, it turns out that the noise is dominated by the thermal fluctuations of the holes within the base and the exact determination of the base noise resistance is a prerequisite for accurate compact noise modeling. It is shown that the base noise resistance equals the base resistance and can be evaluated with standard parameter extraction schemes. Based on an accurate base resistance the SPICE model yields good results as long as the frequency is considerably below the peak cutoff frequency. The unified model, on the other hand, is found to yield good results even at frequencies comparable to the peak cutoff frequency. But this is achieved at the expense of an additional parameter which is difficult to determine without physics-based numerical noise simulation. Moreover, it is shown that the drift-diffusion model should not be used to assess the accuracy of compact noise models, because it yields erroneous noise results for state-of-the-art SiGe HBTs.

Date Published: 25 May 2004
PDF: 12 pages
Proc. SPIE 5470, Noise in Devices and Circuits II, (25 May 2004); doi: 10.1117/12.545991

Published in SPIE Proceedings Vol. 5470:
Noise in Devices and Circuits II
Francois Danneville; Fabrizio Bonani; M. Jamal Deen; Michael E. Levinshtein, Editor(s)