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This paper reports on the operating principles, along with design and fabrication considerations, of a novel direct conversion X-ray image sensor based on Mo/a-Si:H Schottky diodes. The choice of Mo as a Schottky contact follows from its relatively low intrinsic mechanical stress, temperature stability, and relatively large X-ray absorption. Furthermore, it is compatible with the standard a Si:H thin film transistor (TFT) technology. Here, the TFTs are intended for use as switching elements in large area imaging applications. Results of X-ray sensitivity are presented for a broad range of X-ray energies (20-100 keV), along with the influence of various geometric and operating parameters on X-ray sensitivity. The detector shows a linear response with respect to the number of absorbed X-ray photons. Analysis shows that the detector sensitivity reaches its maximum for a Mo layer thickness of around 500 nm at 60 kVp. Measurements, performed in a medical environment, demonstrate the feasibility of the detector for large area medical imaging applications 相似文献
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A new model for high bias transport is reported which describes the time-dependent reverse current variations in amorphous silicon Schottky diodes. This phenomenon is of practical importance in the design and optimization of pixels for large-area optical and X-ray imaging. In the model, the main components of the reverse current, namely thermionic emission and tunneling, are both affected by the electric field at the metal/amorphous silicon interface. Time-dependent variations in this electric field arise due to the release of charges trapped in defect states in the depletion region and to charge trapping at the interface. This effect is analyzed using the approximation that the tunneling component of the current is equivalent to a lowering of the potential barrier at the interface. The calculated time-dependent reverse current is compared with the measured data 相似文献
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