Re: Silicon versus GaAs
I think the main reason is there is SO MUCH silicon technology, experience, and fab facilities it is easy to make complex chips from it, whereas GaAs has been generally kept for the fastest of products where you don't have the same density of components but need higher speed. GaAs is more radiation-hard than silicon, but also less tolerant to heat. I'm sure others with more knowledge can provide a better informed answer though.