Hello mwman,
Would be nice to know the real name ;-)
I'm sure cost hase something to do with it, but, if there is a
notcieable performance advantage I expect application's volume mey be a
mitigating factor.
It's always performance per Dollar. Unless there is an application that
simply could not be done at all without SiGe it just has to make
budgetary sense.
After all, GaAs is (much) more expensive than Si, but people willingly
pay for the GaAs performance advantage!
I know SiGe is used for high microwave transistors (HBT), which are
'better' than GaAs transistors (higher ft, gain, est.). Such HBTs are
reltively new (<10years) yet many companies produce tham now as part of
RF/MW ICs.
This is why I was wondering if there are some fundamental disdvantages
for SiGe!
I am not the expert here but a few things are a bit puzzling. Research
results for SiGe diodes had been published a few years ago and IIRC
Philips was involved. However, unless I am missing something I don't see
any products to that effect on their site. Of course, their site ain't
the best so it is easy to miss something. Then they have (had?) their
SiGe wideband transistors BFU510 and BFU540. Both now carry a red
warning flag "This product has been discontinued". Hmm....
Regards, Joerg