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Politics : Formerly About Advanced Micro Devices -- Ignore unavailable to you. Want to Upgrade?

To: Maxwell who wrote (39998)	10/24/1998 6:45:00 PM
From: wily	Respond to of 1574228

Thanks, Maxwell, I seem to have come to the right place. How could the guy who wrote that article have gotten it so wrong? But, when I read the article, and then didn't see any reaction anywhere, I thought that somehow this wasn't really news. Turns out it wasn't even fact. I'm going to email that guy your response. Thanks again, wily

To: Maxwell who wrote (39998)	10/25/1998 11:54:00 AM
From: Pravin Kamdar	Respond to of 1574228

Maxwell, You seem to miss the point. 50GHz range is only for one single transistor switching speed. You got that right. That major error also jumped out at me when I initially read the article. Also, if I remember my device physics correctly, SiGe technology is a heterostructure bipolar technology, where the energy band profile is "engineered" by introducing Ge into the lattice to form conduction and valence band discontinuities at the emitter-base junction. These discontinuities provide energy barriers that limit minority carrier injection back into the emitter; that would otherwise lower the emitter efficiency and reduce beta. In the end, this allows you to dope the base very high, so that you can make it very thin and still have an acceptable base resistance (lateral to the base contact). The thin base allows very quick transit times and allows for high switching frequencies. This same approach can be used with GaAs/AlGaAs to attain 200 Ghz switching speeds. All of this benefit without even considering mobility. It should be remembered that Ge is not a dopant. It is introduced to replace a fraction of the Si atoms with the same number of available electrons for bonding, but changing the lattice energy (and mobility). Is SiGe also being used in FET technology solely to leverage its lower mobility? Pravin.