High Sensitivity HARP Photoconversion Film for Solid-State Imager Excellent pictures even of dark scenes

Background and purpose A compact high sensitivity TV camera facilitates news gathering and program production at night and saves costs and energy in the studio by reducing power consumption of lighting. We have been studying improvement of the quantum efficiency of the HARP*1 photoconversion film for use in next-generation solid-state imagers, to realize a camera capable of obtaining high quality pictures even under low lighting conditions. Outline The picture quality deteriorates due to "shot noise" caused by a reduction of incident photons, as the lighting condition becomes poorer. The noise is theoretically unavoidable but, by increasing the quantum efficiency of the imager, it is possible to make this less of a problem. We have developed a HARP film doped with a large amount of tellurium (Te) to increase the quantum efficiency for the green incident light that has a great influence on the picture quality of the color TV camera. Our evaluation of this new film shows that the quantum efficiency at a wavelength of 540 nm is double that of conventional film and the shot noise is reduced by 3 dB. Future activities We are looking for the best Te-doping profile and for other materials that can be used to achieve stable operation and further increase of the quantum efficiency. *1 HARP (High-gain Avalanche Rushing amorphous Photoconductor) : high sensitivity photoconversion film utilizing avalanche multiplication effect

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