This paper studies the effect of emitter width on the dc current gain, βF , and ac figures of merit, cut-off frequency, f T, and maximum oscillation frequency, f max, of realistic structures for 200 GHz SiGe heterojunction bipolar transistors (HBTs) using two-dimensional drift-diffusion (DD), hydrodynamic (HD) and energy balance (EB) simulations. The carrier transport models used are briefly presented. The SiGe-HBTs studied have a base thickness of 15 nm. Results of the three transport models are shown and analyzed, for the different emitter geometries.