Ultrasmooth, High Electron Mobility Amorphous In–Zn–O Films Grown by Atomic Layer Deposition

Abstract

Ultrasmooth and highly conductive amorphous In–Zn–O (a-IZO) films are grown by atomic layer deposition (ALD). This opens a new pathway to highly transparent and conductive oxides with an extreme conformality. In this process, a-IZO films of various compositions are deposited by alternate stacking of ZnO and In2O3 atomic-layers at a temperature of 200 °C. The IZO films have an amorphous phase over a wide composition range, 43.2–91.5 at %, of In cation ratio. The In-rich a-IZO film (83.2 at % In) exhibits a very low resistivity of 3.9 × 10–4 Ω cm and extremely high electron mobility in excess of 50 cm2 V–1 s–1, one of the highest among the reported ALD-grown transparent conducting oxides. Moreover, it exhibits an ultrasmooth surface (∼0.2 nm in root-mean-square roughness), and can be conformally coated onto nanotrench structures (inlet size: 25 nm) with excellent step coverage of 96%.