New solid-state image pickup devices using photosensitive chalcogenide glass film

A new solid-state imager, in which the photosensitive Se-As-Te chalcogenide layer is separated from and deposited on the Si scanning array, has been fabricated and successfully operated. The n-MOS FET array used as a scanner has 320(H) × 244 (V) scanning elements and each element measures 27 µm by 27 µm. New processes such as the heat treatment of the photoconductive film during its evaporation, and the low temperature deposition of a transparent electrode, have made it possible to obtain defect-free imaging devices. Applying a target voltage of 40 V to the transparent electrode, we have obtained high sensitivity over the whole visible region. A blue(450 nm) sensitivity of 0.2 µA/µW obtained with this sensor is comparable to the tube sensitivity using the same target film. An SN ratio greater than 40 dB has been realized. Without any special antiblooming control, blooming phenomenon has been suppressed up to the scene illumination over 20 Klx(f4).