An Analysis of the Anomalous Dip in Scattering Parameter of InGaP–GaAs Heterojunction Bipolar Transistors (HBTs)

The kink phenomenon in scattering parameter of
InGaP–GaAs heterojunction bipolar transistors (HBTs) was explained
quantitatively for the first time. Our results show that the output
impedance of InGaP–GaAs HBTs can be represented by a simple series
resistance–capacitance ( – ) circuit at low frequencies and a simple
parallel – circuit at high frequencies very accurately because of the
high output resistance of HBTs. The behavior of of HBTs is in contrast
with that of field effect transistors (FETs), where the smaller drain–source
output resistance obscures the ambivalent characteristics.