An analysis of the anomalous dip in scattering parameter S22 of InGaP-GaAs heterojunction bipolar transistors (HBTs)

The kink phenomenon in scattering parameter S22 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 (R-C) circuit at low frequencies and a simple parallel R-C circuit at high frequencies very accurately because of the high output resistance of HBTs. The behavior of S22 of HBTs is in contrast with that of field effect transistors (FETs), where the smaller drain-source output resistance R(ds) obscures the ambivalent characteristics. (Author)