It's more of a PhD in "design thinking" (or insert your favorite
"innovation" buzzword here) than straight up user experience, but as you
noted I don't think you'll find a PhD program in that.
I've know and worked with 2 PhD's from ID (as well as did my undergrad
there, so I'm biased) that I could put you in contact with as well.
FWIW, I've also met a lot of people in the UX profession with PhD in
anthropology as that seems to translate well.
I've been thinking about getting a PhD in some field
that would allow me to study something like User
Experience. I phrase it this way because of the
vocabulary issues -- I doubt that there is such a
thing as a PhD in User Experience, but what avenues
exist such that you can study it under some other
My Master's is in either Information Design and
Technology or (as it became known later) Digital Media
at Georgia Tech and I'm considering further study.