Achievement of a high-mobility FET with a cloud-aligned composite oxide semiconductor

Abstract

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 GaOx and GaZnOx, which contribute to on/off (switching) characteristics, and the other is composed mainly of InOx and InZnOx, 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).