Here's something for those who are having their doubts whether POET Technologies could build a ring oscillator in GaAs at all.

Well, here is one they have built already:

This ring oscillator (actually two of them) must be in 200 nm or so, I think. The nine substructures per ring oscillator should be the inverters.

You can find the image in this EE Times article:

Moore's Law Has No End in Sight – GaAs is VLSI's inevitable successor to silicon

Unfortunately EE Times mixed up the image captions in the article. However, the names of the referenced files are correct.

Bottom line: The ring oscillator as such isn't the challenge, building it at 100 nm is. But since POET Technologies mastered even 40 nm already, a 100 nm ring oscillator should be a done deal. The question is not if, but when.