Heterostructures with hydrogenated amorphous silicon for use in imaging devices

Abstract

Heterostructures with hydrogenated amorphous silicon (a Si:H) and crystalline semiconductor materials such as silicon (c-Si:H), germanium (c Ge), cadmium telluride (CdTe), etc. have been investigated for application to imaging devices. The large valence-band offset ofc-Si/a-i:H heterojunctions was compensated by boron doping in the deposition of a-Si:H and imaging devices with high resolution were demonstrated in the visible and near-infrared region. Inc-Ge/a-Si:H heterojunctions the offset is too large to be compensated by boron doping and to realize IR imaging devices. Finally,c-CdTe/a-Si:H heterojunctions indicated no band offset at the valence side. Using the CdTe heterojunction, a high-sensitivity X-ray image sensor was constructed and demonstrated utilizing its high absorption coefficient. It was shown under the band offset consideration that heterostructures with a Si:H and some kinds of crystalline semiconductors provide promising image sensors covering wide spectral ranges.