Heavy-doping transport parameter set describing consistently the DC and AC behavior of bipolar transistors

Using transistors with opaque polysilicon-emitters, the apparent bandgap narrowing in heavily doped n-type silicon has been measured with a temperature-dependent DC method. Collector currents and forward transit times of polysilicon-emitter transistors with different base doping levels in the heavy-doping region of N/sub A/>or=10/sup 17/ cm/sup -3/ have been determined. Comparing these measured values with simulated ones, different heavy doping parameter sets have been used for modeling. At N/sub D/=1.5*10/sup 20/ cm/sup -3/, the apparent bandgap narrowing is shown to amount to 105 meV. No existing heavy-doping parameter set is able to describe the DC as well as AC behavior of bipolar devices with heavily doped base layers. A new parameter set is suggested which correctly describes the DC and AC characteristics of these devices with a maximum uncertainty of about 30%.<>