But … GaAs is the material of the future … and always will be …

I read a note on IBM’s recent allocation of capital towards research projects. It had this tidbit in there:

III-V technologies
IBM researchers have demonstrated the world?s highest transconductance on a self-aligned III-V channel metal-oxide semiconductor (MOS) field-effect transistors (FETs) device structure that is compatible with CMOS scaling. These materials and structural innovation are expected to pave path for technology scaling at 7nm and beyond. With more than an order of magnitude higher electron mobility than silicon, integrating III-V materials into CMOS enables higher performance at lower power density, allowing for an extension to power/performance scaling to meet the demands of cloud computing and big data systems.

Well, there are a range of III-V materials. Not just GaAs.
One of the big issues is the lattice mis-match between SI and many of the III-V material. This strain introduces “artifacts” in the bandstructure, not to mention structural morphologies. This said, those artifacts may be what the engineers want. Aluminum Phosphate and Gallium Phosphate are pretty well matched to SI. And the other properties aren’t bad.
But alas, AlP is quite toxic. GaP is possible, and has a similar growth process as with Silicon wafers. Its used in LED applications today. InP is also quite possible and it is used today in other optical applications, such as laser diodes.
I remember that GaAs/InGaAs systems were starting to become interesting around the time I had finished up. I am not unhappy with the direction I took away from this, though it is interesting to review where its gone in the last 18 years since I was more seriously involved.