SiOnyx is set up to commercialize the new material discovered by Harward University physicist Eric Mazur. As I understand from the company site "Black Silicon" is a modified material having a narrower than bulk Si bandgap and still compatible with Si process (not necessarily CMOS process). The narrower bandgap allows for higher absorption coefficient for visible light.
It looks like the photodetector is based on photoconductive principle, rather than photodiode, so an additional gain is possible right in the detector itself. The noise would be higher as well, both at low and strong light, but the company does not talk about this so far.
SiOnyx sees a lot of applications for the new photodetector, imaging is one of them. A white paper specifically talks about smaller than 1um pixels, leveraging higher absorption coefficient of Black Silicon.
NY Times runs an article about the new company and people behind it.