Why not SiGe Microwave Schottky Diodes?

Can anyone explain why people use Si and Ga As for microwave/RF Schottky diodes and not SiGe?

For Si versus SiGe that probably boils down to one single sign: $

Regards, Joerg

Thank you, Joerg!

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.

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 (

Hello mwman,

Would be nice to know the real name ;-)

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.

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

Thank you for your reply, I found it very informative.

I'm looking for a small subcontarctor to test for us microwave diodes and capacitors: do you 'or someone you know' knows one in the Silicon Valley?

Regards,

Adrian

Hello Adrian,

I had seen your other post, would have answered if I knew someone with an impedance analyzer that can go to 35GHz. Mine is limited to 1GHz. You might want to scope through the IEEE consultant's database and look for microwave folks in California:

The other option might be to rent an analyzer from a company like Telogy and do it in-house.

Regards, Joerg