Improved analytical method for determination of small-signal equivalent-circuit model parameters for InP/InGaAs HBTs

An improved direct extraction method for determination of the small-signal equivalent-circuit model for InP/InGaAs double heterojunction bipolar transistors is presented. This method is based on an accurate small-signal model, which takes into account the base-emitter and collector-emitter metalisations by using two additional capacitances C/sub mb/ and C/sub mc/. These capacitances (C/sub mb/ and C/sub mc/) are extracted using a set of exact closed-form equations. Significant improvement of the extraction accuracy of the intrinsic base-emitter junction capacitance C/sub be/ is obtained by using the new combination method, which is based on the relationship between the conventional T- and PI-type equivalent-circuit topology. The approach has been verified over a wide range of bias points using an InP HBT with 5/spl times/5 /spl mu/m/sup 2/ emitter area in the frequency range of 50 MHz-40 GHz.