Two-dimensional a-Si:H n-i-p photodiode array for low-level light detection

This paper presents the design, fabrication process, and performance evaluation of a two-dimensional hydrogenated amorphous silicon (a-Si:H) n-i-p photodiode array, developed specifically for low-level light sensor applications. The design of the device is simpler than conventional active-matrix-arrays based on thin-film transistor (TFT) addressing electronics, owing to the utilization of the a-Si:H switching diodes for signal readout. The discussed technological developments are aimed to minimize the leakage current and to enhance the external quantum efficiency. The current-voltage characteristics of the sensing and switching diodes are analyzed to identify the sources of the excess leakage current. The optical losses in the photodiodes with an ITO/a-SiN_x:H antireflection coating have been minimized using numerical modeling. Description of the peripheral electronics and associated timing diagrams along with the results of the detector characterization, including the linearity and response time measurements, are presented and discussed.