My knowledge is not extensive enough to give a conclusive answer to that, but I think you can, under certain conditions. Although there will be delays in transmitting data or signals, because GaAs is much faster than Si as each metal has their own properties. Yes Intel is exclusively Si based and IBM is still spending billions of $$ each year of research in Si, and if they don't adapt to a superior technology they will be left behind. I believe that one of the I-Phone's is already using GaAs based technology, and hopefully other manufacturers will follow suit.
There will be an overlapping transitional period between Si & GaAs tech and this is already in progress as Si is nearing the end of its capabilities. Maybe with nano-technology they can squeeze a few bits & bytes out of it but the new technology will be much more efficient in so many ways that they'll have to leave the old tech behind. Some big name companies will stubbornly stay with Si and be blind for the new tech coming thru, and those will be the one that miss the boat and dwindle in the abyss of oblivion. Of course this will happen over a multiple year span but just like with evolution, if you don't adapt you get extinct...
GO OPL ;-)
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