Dual-Gate Photosensitive Thin-Film Transistor-Based Active Pixel Sensor for Indirect-Conversion X-Ray Imaging

Over the past century, the conventional film-based radiographic X-ray imaging has evolved into digital radiography (DR). Amorphous silicon thin-film transistor (TFT)-based flat panel X-ray detector was introduced two decades ago, and has become a ubiquitous platform for several imaging modalities, including chest radiography, mammography, and fluoroscopy. As a fundamental building block, an advanced pixel has thus been developed to tackle clinical challenges. However, all types of pixel architectures, either passive or active, unanimously keep sensing, storage, and readout components separate. This is disadvantageous in further reducing pixel size and improving spatial resolution. To address these problems, we hereby propose a novel architecture, which combines the abovementioned three functional units in one single dual-gate photo-TFT. In other words, the dual-gate photo-TFT alone works as a sensor, a storage, and a switch. In addition, by harnessing the amplification effect of TFT, it, for the first time, realizes one single-transistor active pixel sensor that makes a tremendous promise in achieving low-dose X-ray imaging for DR. In this paper, the proof-of-concept device was fabricated using the conventional amorphous silicon TFT technology and the device was characterized in a series of measurements of electrical and optoelectronic performance.