Silicon Investor (SI) -- The First Internet Community

STOCKTALK

We've detected that you're using an ad content blocking browser plug-in or feature. Ads provide a critical source of revenue to the continued operation of Silicon Investor. We ask that you disable ad blocking while on Silicon Investor in the best interests of our community. If you are not using an ad blocker but are still receiving this message, make sure your browser's tracking protection is set to the 'standard' level.

Technology Stocks : George Gilder - Forbes ASAP -- Ignore unavailable to you. Want to Upgrade?

To: George Gilder who wrote (299)	2/16/1998 11:20:00 AM
From: Nevin S.	Respond to of 5853

Thanks for the reply

To: George Gilder who wrote (299)	2/16/1998 6:36:00 PM
From: Tim Bagwell	Respond to of 5853

George, SiGe transistors have a long way to go before they are a serious threat to GaAs. For one thing, the data I've seen for SiGe shows that ft maxes out at at low collector currents around 1 mA. The ft falls off quickly at higher currents. This implies that the devices are not useful for power applications which is where GaAs excels. Also, they may not be useful for applications that require large slew rates. So if you are building a wireless radio that needs a power amplifier for the transmitter it's far better to have both the receiver and transmitter on one IC than to mix and match technologies. Second, SiGe has been shown to have ft's near 50GHz in production (at low collector current). However, this is only roughly a doubling over current state-of-the-art silicon processes without a heterojunction. Is this enough of an advantage to supplant GaAs? I doubt it. Third, GaAs has matured over its 20 or so years of research and development. Heterojunction devices, when used in GaAs, can have ft's well over 100 GHz in production. SiGe still has a long way to go --probably about 10-15 years. And last, I have yet to see any reliability data on SiGe. Germanium is a problematic material in silicon and even more so as the basis for a heterojunction. There are subtle drift mechanisms that can occur in such devices. I would not place any faith in these devices until I see that thousands of hours of high temperature accelerated testing has been undertaken to prove the stability of the materials. GaAs will be with us for the forseeable future and will be the material system of choice for wireless radio.