No.109 May 2008

Paper

  • 15-μm-thick HARP Photoconductive Film
    Yuji OHKAWA, Kazunori MIYAKAWA, Tomoki MATSUBARA, Kenji KIKUCHI, Shirou SUZUKI, Misao KUBOTA and Norifumi EGAMI
    ↓summary

    summary
    High-sensitivity HARP photoconductive film, which makes use of the avalanche multiplication phenomenon, was investigated for the purpose of reporting breaking news at night or producing nature and science programs. HARP films that are thicker and more sensitive than the previous 8-μm-thick one were studied. Thickening the HARP film causes a problem whereby defects easily appear during shooting intense spot lights. It was found that controlling the operation temperature(over 30°C) of the 15-μm-thick HARP film prevents the occurrence of defects. Moreover, the heat resistance of the film was improved so as to resist temperatures over 30°C. A reliable 15-μm-thick HARP film whose avalanche multiplication factor is about 200 was developed.
  • 1-inch 256*192 Pixel HARP Image Sensor with Active-matrix HEED
    Masakazu NANBA, Yuki HONDA, Yoshiyuki HIRANO, Kazunori MIYAKAWA, Toshihisa WATABE, Saburo OKAZAKI, Yoshiro TAKIGUCHI, Norifumi EGAMI
    ↓summary

    summary
    We developed an active-matrix high-efficiency electron emission device(HEED) that had scanning driver circuits fabricated with conventional MOS planer technology. A 1-inch 256*192 pixel image sensor, consisting of the active-matrix HEED and a high-gain avalanche rushing amorphous photoconductor(HARP) target, was fabricated and tested as a step toward the development of ultrahigh-sensitivity compact image sensors with a large number of pixels. The experimental results show that the prototype sensor can be used to obtain clear images even under dark lighting conditions, such as in moonlight, and that the active-matrix HEED is a promising high-speed image pick-up device.
  • Color separation characteristics of stacked organic photoconductors
    Hokuto SEO, Satoshi AIHARA, Toshihisa WATABE, Hiroshi OHTAKE, Misao KUBOTA and Norifumi EGAMI
    ↓summary

    summary
    With the aim of developing compact and high-resolution single-plate color camera, a new type of image sensor overlaid with three organic photoconductive films each sensitive to only one of the primary color components was studied. To verify the principle of color imaging in the vertically stacked structure of organic photoconductive films, we fabricated three organic photodetectors composed of blue, green and red sensitive organic photoconductive films on individual glass substrates, and stacked these detectors. Spectral photoresponse characteristics for the stacked structure revealed that the output signal from each detector had good spectral selectivity, clearly demonstrating color separation in the vertically stacked structure of organic photoconductive films.