Development of High Sensitivity 15-.MU.m-thick HARP Photoconductive Film with Higher Photoelectric-conversion Efficiency for Red Light

HARP (High-gain Avalanche Rushing amorphous Photoconductor) photoconductive films have high sensitivity by means of avalanche multiplication in amorphous selenium (a-Se) . A 15-μm-thick HARP photoconductive film that has a photoelectric-conversion efficiency for red light that is twice that of the conventional one has been developed. The HARP film, which mainly consists of a-Se with a band gap of about 2.0 eV, does not have sufficient photoelectric-conversion efficiency for red light. To solve this problem, the film is doped with Te with a band gap of about 0.3 eV. Doping a-Se with a larger amount of Te increases the efficiency. However, it can also deteriorate characteristics such as dark current, defect occurrence, and lag, because it creates many trap levels for electrons in the Te-doped a-Se layer. Trapped electrons increase the internal electric field around the incidentlight-side interface. We investigated Te-doping conditions that would not cause these problems.