Bias dependence study of the HBT small-signal equivalent circuit elements using a new parameter extraction technique

An improved HBT small-signal parameter extraction procedure is presented in which all the equivalent circuit elements are extracted analytically without reference to numerical optimisation. This parameter extraction technique is applied to InGaP-GaAs DHBTs and it is shown that the agreement between the measured and simulated S- and Z-parameters in the entire range of frequency is excellent such that an optimisation step following the analytical extraction procedure is not necessary. Bias dependence of various small-signal parameters is studied. High current effects such as B-C capacitance reduction, base pushout, and device self-heating are observed experimentally and explained in terms of device physics and parameters.