A new pixel architecture, PMOS-reset Active Pixel Sensor, was built on SOI substrate in order to overcome the limit of output voltage swing because of V_DD scaling. The photodiode was built on a substrate and the reset transistor and in-pixel amplifying transistor were built on the top silicon film. Compared with the bulk implementation, SOI technology allows the bulk photodiode to be optimized for efficiency through the use of lightly doped SOI substrate, without compromising circuit’s performance. At the same time, the replacement of NMOSFET reset transistor with a PMOSFET does not need to introduce an N-well, thus conserving the area of the pixel....[ Read more ]

A new pixel architecture, PMOS-reset Active Pixel Sensor, was built on SOI substrate in order to overcome the limit of output voltage swing because of V_DD scaling. The photodiode was built on a substrate and the reset transistor and in-pixel amplifying transistor were built on the top silicon film. Compared with the bulk implementation, SOI technology allows the bulk photodiode to be optimized for efficiency through the use of lightly doped SOI substrate, without compromising circuit’s performance. At the same time, the replacement of NMOSFET reset transistor with a PMOSFET does not need to introduce an N-well, thus conserving the area of the pixel.

Active pixel sensors were also built on Silicon-On-Sapphire substrate and worked under backside illumination. There were three different kinds of Active Pixel Sensors built on SOS substrate with three different kinds of photosensitive elements: the PIN diode, the N-diode and the P-diode. Performances of the three photosensitive elements were compared and the output characteristics of pixels with these three elements were obtained. The pixel with the PIN diode was proved to be the best performing one under the same illumination intensity.