Characteristics of Cr Schottky amorphous silicon photodiodes and their application to linear image sensors

摘要

Cr Schottky amorphous silicon (a-Si:H) photodiodes with a configuration of Cr/a-Si:H tin-doped indium oxide (ITO), where Cr is negatively biased with respect to ITO in contrast to the conventional bias direction, were characterized to provide simple and stable sensor elements for economical linear image sensors. It was found that the barrier height of the Cr/a-Si:H junction is sufficiently high (0.89 eV) to prevent electron injection and that the junction is thermally stable. The transport properties of holes propagating in the a-Si:H layer were largely improved by a few parts per million boron doping, and as a result saturation of the photocurrent was achieved. A contact-type ISO A4, 8-dot/mm linear range sensor was fabricated using the Cr Schottky photodiode array. The sensor showed excellent characteristics for use in G3 facsimile.