Reliability of Gap-Type Thin Film Transistors Under Low Illumination for Imaging Sensing Applications

Abstract

In large-area image sensing applications, such as under-display fingerprint sensors, amorphous silicon (a-Si) gap-type thin-film transistors (TFTs) are favored due to their simple fabrication process and high sensing current. These applications typically involve device operation under low-light illumination conditions. Despite these advantages, the recovery behavior of performance parameters after exposure to stress factors, including bias stress and photo-stress, has not been comprehensively explored, particularly in relation to reliability recovery. This study systematically investigates the impact of fixed-bias and pulsed-stress operations under low-light conditions. The experimental findings are further analyzed using Technology Computer-Aided Design (TCAD) simulations to elucidate the underlying mechanisms. Results indicate that long-term bias stress induces significant variations in the photocurrent characteristics of the devices. However, the introduction of pulsed operations in sensing applications markedly enhances the operational lifetime of the devices, offering a promising pathway to improving their reliability.