3.1: Invited Paper: Amorphous Oxide TFTs: Progress and Issues

This paper discusses progress and issues related to amorphous oxide semiconductors (AOS) thin film transistors (TFTs) for flat panel display and imaging applications. In particular, we review the dark- and wavelength-dependent photo-instability in AOS TFTs and its origins, along with the density of states (DOS) profile in these materials, including the role of oxygen vacancies. The relative dominance of trap-limited conduction (TLC) and percolation depending on gate voltage is presented. The effects of photo-instability and specifically persistent photoconductivity (PPC) arising from ionized oxygen vacancies is examined using results of stress/recovery measurements. Based on this, techniques to overcome the PPC are presented, and includes a dual gate photo-TFT structure with appropriate pulse biasing.

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