Re: SiGe Technology
SiGe is a BiCMOS technology. So, you have the option to use bipolar transistors ( vertical bipolar transistors ). Usually, these BJT's have a much higher fT ( maybe an order of magnitude higher )than the CMOS transistors so they can be used for higher frequencies.
I don't think there is a special consideration. You just have the option to use very high speed Bipolars besides the normal MOS transistors.
Just take care of the limitations of BJT's, namely: base current, larger areas, limited swing, and relatively high Vbe ( may reach 0.8 - 0.9 Volts which may cause headroom limitations ).
Regards