Evaluating and designing the optimal 2D collector profile for a 300Â GHz SiGe HBT

An optimally designed selectively implanted collector (SIC) doping profile allows keeping a SiGe-HBT's current in a vertical flow under the emitter while minimizing the parasitic collector-base capacitance (Ccb). TCAD simulations were used to provide insight into a 300 GHz HBT's current flow lines and to derive design guidelines for the optimal mask width of the SIC implant. This boosted the HBT's transit frequency (ft) by 6.5% and the unity power gain (fmax) by 23%.