Tailored Laser scanned photodiodes (LSP) for image recognition

Abstract

ABSTRACTA tailored ZnO:Al/a-p-i-n SiC:H/Al configuration for the laser scanned photodiode (LSP) imaging detector is proposed. The LSP utilizes light modulated depletion layers as detector and a laser beam for readout. When highly resistive a-SiC:H doped layers are used its higher optical gap when compared with the active layer are responsible by charge accumulation at the illuminated interfaces which blocks the carrier collection under illumination. Those insulator-like layers act as MIS structures that prevent excess signal charge from blooming to the nearby dark regions avoiding the image smearing.The optical-to-electrical transfer characteristics show reciprocity between light intensity and image signal intensity only limited by the doped layers composition. Data reveal that the sensitivity, the responsivity and the spatial resolution are limited by the cell configuration while the linearity depends on the light source flux used to map the image onto the sensor. By using tailored SiC:H/Si:H/SiC:H p-i-n heterostructures an increase in the image signal optimized to the blue is achieved with a responsivity of 0.2 mW/cm2 and a spatial resolution of 20 µm.