Integrated amorphous silicon photoconductive type image sensor

The authors report a study on an integrated amorphous silicon photoconductive-type image sensor. The photoconductive-type sensor has the advantage of a high photocurrent. All the elements in an integrated sensor circuit, including sensor, storage capacitor, switch transistor, and matrix wiring, can be fabricated within one deposition process. A novel sandwich structure with a low level-phosphorous-doped layer is proposed to enhance the photoconductivity. A high photoconductivity of 5×10^-5 S cm^-1 has been achieved, with a photosensitivity of 5×10⁴. The key to the sensor is the SiN/a-Si:H interface, which can be controlled by a metal gate underneath the SiN layer. The thin-film transistor with low-level doping in the channel material has an on current of 1 μA and an on/of ratio of 10 ⁴