ITO/a-SiN_x:H/a-Si:H Photodiode with Enhanced Photosensitivity and Reduced Leakage Current Using Polycrystalline ITO Deposited at Room Temperature

摘要

We report an ITO/a-SiN_x:H/a-Si:H MIS photodiode structure based on room temperature deposition of optically transparent polycrstalline ITO for applications in large area optical and x-ray imaging. The photodiode structure exhibits device characteristics with reduced leakage current and enhanced photosensitivity giving rise to a hundred-fold improvement in dynamic range. This notable improvement in performance is believed to be due to the reduced diffusion of oxygen from the ITO to the a-Si:H layer, and thus reducing the density of defect states inside the a-Si:H layer. The behavior of photo and dark current is consistent with an elaborate transport model for the Schottky barrier. The model agrees reasonably well with measurement data for the dark current and provides a consistent picture in terms of the photo current behavior in the MIS structure, where the insulating layer serves to reduce the oxygen diffusion.