Design of SiGe/Si heterojunction bipolar transistor for RF mixer application

The design and simulation of NPN SiGe/Si heterojunction bipolar transistors (HBTs) suitable for RF mixer application are addressed. The feasibility of using the computer to simulate extensively from the fabrication process to the circuit application is also investigated. The process simulator TSUPREM, rather than the actual measured data, was used to obtain the doping profiles of the SiGe/Si HBTs, which were then input to the MEDICI 2D simulator to simulate device characteristics. The influence of Ge profiles, doping concentrations and device geometries on the DC and AC performances of the SiGe/Si HBTs are simulated. Base on simulation results, an optimum SiGe/Si HBT suitable for RF mixer application was determined. The Gummel-Poon model parameters extracted from the optimized HBT are then used in the analysis of a Gilbert-cell mixer circuit operated at 2.45 GHz by the ADS high-frequency circuit design tool