A photo detector with enhanced charge storage capacity for 2D image applications

An innovative photo detector structure with the enhanced charge storage capacity for two-dimensional image applications has been investigated in this work. Although the structure of the detector is very simple that an additional insulation layer is inserted between the metal electrode and the p- or n-layer of a photo diode, the charge storage capacitance can be increased up to 4 times of the junction capacitance of a reverse biased amorphous silicon p-i-n diode. The enhanced charge storage capacity of each pixel conducts that the signal dynamic range of a two-dimensional image array to be increased, and the linearity as well as the data retention time be also increased. Based on this structure, the performance of a hydrogenated amorphous silicon p-i-n photodiode, with a silicon nitride insulator layer, coupled with calcium tungstate scintillator acts as an x-ray detector was reported in this paper.