Vertical ITO/SiOX/a-Si:H Photodiode-Gated Low-Temperature Polycrystalline Silicon Thin-Film Transistor Intended for In-Display Fingerprint Imaging Applications

To embed an active pixel optical sensor in a display pixel for fingerprint imaging, an area-efficient and vertical ITO/SiOX/a-Si:H photodiode-gated low-temperature polycrystalline silicon dual-gate thin-film transistor with controllable photosensitivity is proposed and experimentally demonstrated. The device can be operated as a driving switch to the display pixel, and the driving current is insensitive to normal ambient light; the device can also be operated as an optical sensor, which provides 8 bits of effective data and reasonable detectable intensity range. The compact structure and dual-mode operation make it a promising solution to in-display, large-area fingerprint identification for smartphones.