It’s the perennial question (or one of them): how long can silicon last?
Without giving dates, imec’s Rudy Lauwereins opined that silicon will be replaced by GaAs and by germanium.
This is like back to the future in two different ways. Germanium was the semiconductor of choice before silicon was taken up – back when few were actually making a choice. Meanwhile, GaAs was supposed to take over many years ago, and silicon refused to yield its premier position.
One of the things that gives silicon an edge is its cost: ingots of GaAs and germanium will be expensive. Which is why that’s not what imec sees coming. They see deposition (not transfer) of the materials on silicon. Why waste expensive materials on what is essentially an inactive substrate?
But, you point out… you’re going to have a hard time matching the lattices between the silicon substrate and the deposited active layer. This is true, and it’s where much of the work is being done. But that mismatch can actually be useful, providing strain that improves performance.
They are apparently working this with an unnamed company, preparing a fab transfer..