Abstract




Large area electronics aims to build electronic systems in large area format and at low cost. One of popular applications is flat panel displays that are widely deployed in consumer electronics. Large area imaging has also become an integral part of large area electronics where flat panel X-ray detector, optical fingerprint sensor, and biomedical fluorescent imaging are emerged. In large area imaging, pixel technology based on thin-film photodetectors and transistors is essential, enabling high sensitivity, high spatial and time resolution to address requirements of various applications. A conventional pixel usually consists of a photodetector such as photodiode or similar as a sensor and a thin-film transistor (TFT) as a readout switch in the passive pixel sensor (PPS) architecture. However, it suffers from low signal to noise ratio (SNR). To improve the SNR, an active pixel sensor (APS) including a photodetector and multiple TFTs was proposed by introducing in-pixel amplification. However, it trades off the spatial resolution as a result of planar integration where the photodetector and TFTs are kept separate laterally.


Therefore, advanced pixel technologies that have high SNR and high spatial resolution are on demand. In order to achieve both, a 3-D APS architecture is proposed where the photodetector is vertically integrated atop the TFT. In this talk, a few 3-D APSs based on amorphous silicon, low-temperature polycrystalline silicon, and spherical silicon material systems will be presented along with mechanisms that lead to high sensitivity and high spatial resolution.