Samsung patent application US20100320515 proposes a single-electron JFET-like structure (SEFET) to make small and sensitive pixel:
The photoelectrons are collected in N-doped area and drift close to the p-channel area due to the doping gradient. Then the collected electrons modulate the channel conduction by changing the N-gate potential:
Few different readout schemes are proposed, for example, this one (Vin is N-doped area voltage):
One thing I was unable to find in the Samsung application is how the N-doped gate is reset before the integration starts.
Pixart application US20100320552 proposes to place color filter on top of microlens to improve the light passage through the metal stake:
"Compared with the prior art, such arrangement is advantageous in that the micro lens 18 is located much closer to the photo diode 12. As a result, the micro lens 18 has a wider chief ray angle, and the photo diode 12 has a better light collection efficiency."