who is the supplier of Touch Screen controller?

The iPhone is designed in California, and I know the iPhone is manufactured by Foxconn, so I would guess that part is manufactured by them under the Apple design plans. There isn't a whole lot of information about specific parts other than the A4/A5 chips being designed by Samsung.

I don't think we will have that information aside from apple. There are substitutes for it but if you want a genuine replacement, it needs to come from Apple.