The microwave performance of SiGe Si HBTs and amplifiers

In this paper, we analyze the SiGe/SiHBTs microwave performance including the following factors:(1)when the bar width reduce to lower hundreds angstromt the emitter delay time and the collector delay time became more important factors of the cut off frequency f(T) of SiGeHBTs,(2)the influence of the low doping emitter layer to the emitter delay time, (3)besides the capacitance resulting from the change of the fixed charges in the heterojunction, the free carrier injection in the emitter base space charge region result additional capacitance, for an heterojunction operating at forward bias, (4)hence, we give the equal circuits of SiGeHBTs, analyze and optimize the cut off frequency of SiGeHBTs, and simulate the microwave performance of SiGeHBTs and its amplifier. The novel f(T)=10GHz SiGeHBTs and amplifier have been fabricated, the results of test are in fit with the ones of simulation.