I. Introduction
For the next-generation devices, it is required to develop large-area, high-resolution, high-framerate displays [1], [2], [3]. Thus, the oxide thin-film transistor (TFT) used as the switching and driving elements of the display should exhibit a high ON-current at the supply bias voltage of 5 V [4]. Since the Ion of the device is proportional to the mobility of the electronically active oxide semiconductor channel, various research has been conducted to increase its mobility in oxide semiconductor TFT by employing metal doping, [5] heterostructure stack, [6] and changing the atomic ratio of the oxide channel [7]. However, it is difficult to resolve issues regarding reliability degradation such as negative threshold voltage () shifts and instabilities [8]. As an alternative, high- gate insulators can be used for developing high- devices, provided that the reliability and quality of the interfacial layer are guaranteed. Particularly, in the past ten years, hafnia-based oxide film has attracted a lot of interest as a potential technique for high- gate insulators [9], [10], [11], [12]. Benefits of hafnia-based oxide film include a wide bandgap, low equivalent oxide thickness (EOT), facile atomic layer deposition (ALD) deposition, high dielectric (DE) constant ( 20), and excellent compatibility with the CMOS process [13], [14].