We have recently discovered that films of a widely used In–Ga–Zn oxide (IGZO) with have different material composition states when sputter-deposited under different conditions using the same polycrystalline IGZO target. Significant improvements in on-state current and mobility (as high as 40 cm2·V−1·s−1) are obtained. The results of local composition analysis indicate that the deposited film is not composed of any known homogeneous IGZO compound and that the components of this film are separated into two types of nanoparticle regions: one type is composed mainly of GaO x and GaZnO x , which contribute to on/off (switching) characteristics, and the other is composed mainly of InO x and InZnO x , which contribute to on-state characteristics. These regions constitute a new type of oxide semiconductor (OS) film. The nanoparticles with a blurry boundary extend like a cloud, probably complementing one another. We consider that this OS film has a novel composition, which can be described as a “cloud-aligned composite OS” (CAC-OS).

A 13.3-inch 8k4k organic light-emitting diode display based on a newly developed highmobility indium-gallium-zinc-oxide material was fabricated. It was found that the use of a highermobility material decreases the scan driver size and power consumption. Furthermore, such oxide semiconductor layers with a buried channel structure can increase process stability and reliability.

We have fabricated top‐gate field‐effect transistors (FETs) based on an oxide semiconductor for high‐performance driving capability. The optimization of the plasma treatment enabled a 50‐nm‐thick gate insulating film and a short channel length of these FETs, enabling a high FET performance.

A top‐gate self‐aligned transistor with excellent characteristics was developed using a cloud‐aligned composite oxide semiconductor (CAC‐OS). A 1058‐ppi 8K4K foldable organic light‐emitting diode panel was fabricated using the transistor and employing a novel linear laser separation technology. These technologies enable a shift of production lines from low‐temperature polysilicon to CAC‐OS.

A 4.3-inch 1058-ppi 4K liquid crystal display was fabricated using top-gate field-effect transistors (FETs) comprising a cloudaligned composite oxide semiconductor. For transparent pixels comprising an oxide semiconductor/oxide conductor (OS/OC), FETs, wirings, capacitors, and contacts in the pixels are transparent. This display achieves a 63.6 aperture ratio and low power consumption.