Aqueous solution-based synthesis and deposition of crystalline In-Ga-Zn-oxide films with an enhanced mobility

Abstract

In-Ga-Zn-oxide (IGZO), in its amorphous state, is known to have a high electron mobility and low off-state current inside transistor devices, which may even be further improved by crystallization. Thin films of the IGZO superlattice structure require an optimal layer homogeneity in addition to precise control of the stoichiometry, which can be achieved by using a solution-based process. In this work, an aqueous precursor system is developed, starting from the respective metal (hydr)oxides. A stable multimetal precursor is obtained, which is ideally suited for solution-deposition via spin-coating. Through an optimized multi-step thermal treatment, crystalline thin films of IGZO are obtained that show a preferential c-axis orientation after rapid-thermal annealing at 1000 °C in inert conditions. The resulting film shows a good optical transparency (>70%) and an improved carrier mobility (27.2 cm²/Vs) compared to typical solution-processed amorphous IGZO films, and is therefore promising for further application.