Extraction of high-frequency equivalent network parameters of HBT´s by low-frequency extrapolation of microwave S-parameter data

This paper reports a comprehensive low-frequency extrapolation method for the purpose of separating the intrinsic and extrinsic or parasitic equivalent network parameters of high-frequency HBT´s. The method involves measurements of the device´s small-signal parameters over a wide frequency range, and low-frequency extrapolation (LFE) of various transformed two-port parameters using a range of collector bias currents. For the extraction of the equivalent network parameters, the measured S-parameters are first converted into y- and h-parameters and they are used directly or in composite fashions in order to extract the parasitic series resistance elements (r_bb´, and r_ee´ ), the shunt capacitance elements (c_je, c_bc and c_c), and the intrinsic emitter-to-collector transit time after allowing for the parasitic time constant effects