Design of an Ultrasensitive Active Pixel Sensor that is based on Silicon Nanostructures

The standard noise-related performance limit of a typical image sensor, especially for detection from a weak source, is set by the temporal noise in the pixel. In many applications the background noise is extremely small; the photon noise is smaller than the electronic noise. In addition the pixel noise dominates the noise that is due to the rest of the Read-Out Integrated Circuit (ROIC). To date it has not been possible to attack the fundamental source of noise in the pixel. In this work we turn away from the basic mosfet circuits, and look towards charging effects in nanoscale devices as a way to improve the basic sensitivity. We have designed a novel active pixel sensor that is based on silicon nanostructures, and silicon single-electron amplifiers. Analysis of the detector shows that the noise referred to the input can be in the subelectron regime, and a factor of thirty smaller than for a typical detector which is based on conventional mosfets. A preliminary design of the entire image sensor chip has been completed. The work included 1) design of the pixel array control logic, 2) design of the readout circuitry, and 3) the output Interface logic. Progress on the fabrication will also be discussed.