SiGe VCO

I want to kown the differences between SiGe and Si technologies for the design of the VCO topology

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

khouly

SiGe has lower flicker noise contribution to close-in phase noise.

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?