SiGe technology is a BICMOS technology that include HBT "hetrojunction Bipolar Transisitor" the base of this tarnsistor is a SiGe which make the devices very fast FT typically about 60 to 70 GHz
so u can use these HBT's in VCO desing like cmos cross coupled pair
I did not think that SiGe had lower flicker noise than Si. SiGe works at higher frequency, but adding that doping would raise the flicker noise in SiGe, would it not?