Application of hydrogenated amorphous silicon in charge-coupled devices

Theoretical and experimental studies in the application of a-Si:H to charge-coupled devices (CCDs) are summarized and recent results are presented. The device operates in a new mode where transient signal electrons are stored in the accumulation state of the a-Si:H/insulator interface. Taking multitrapping effects of electrons by localized states into account, charge transfer characteristics have been analyzed. It is shown that the clock frequency can be increased without degradation of the transfer efficiency by shortening the transit time of conduction electrons. The first a-Si:H CCD operation has been confirmed experimentally by an insulator/a-Si:H/insulator structure sandwiched between staggered transfer electrodes. Then, the improved device structure with resistively connected transfer electrodes has been developed. The device operated with the transfer efficiency of more than 99%/ transfer at clock frequencies between 1kHz and 200kHz.