Samsung applied for a patent on speeding-up charge transfer in bi-directional pinned PD to make it fit for ToF sensors. The patent application US20120175685 is authored by Kim Seong Jin, Han Sang Wook, and, surprise, Albert Theuwissen. There is a number of different pinned PD described that create an internal electric field to speed up photoelectrons transfer to both FD0 and FD1 nodes. Some pixel layouts are shown below:
Once we are at high speed charge transfer pixels, there is another recently published application US20120168609 by Alex Krimsky, Luxima. He proposes to place both transfer gates on the same side of the PD and modulate the PD doping to achieve the speedup:
