An Improved EM-Simulation Procedure to Extract Extrinsic Elements of Terahertz InP DHBTs

For accurate small-signal modeling of double heterojunction bipolar transistors (DHBT), electromagnetic (EM) simulations of the outer shell of the DHBT are used for de-embedding the external parasitic parameters. However, under different simulation setup conditions, the parasitic elements can be overestimated or underestimated. This paper presents a systematic approach to set up an EM simulation and obtain accurate parasitic elements of DHBT devices using Ansys high-frequency structure simulator (HFSS). An innovative simulation method is also introduced in order to calculate parasitic base capacitance (Cpb) and base-collector capacitance (Cpbc), which cannot be extracted accurately from “off-state” measurements. Finally, the EM simulation de-embedded small-signal model is found to provide a good fit to the measured data from 50 MHz to 150 GHz.