Metal oxides have risen to prominence in recent years as a promising active layer for thin film transistors (TFTs). One of the main reasons for this has been its value in display technology. Conventionally, displays have relied on amorphous hydrogenated silicon (a-Si:H) TFTs but the demand for large area displays with high resolution, fast response time, low power consumption and compatibility with integrated driving circuits have prompted research into other semiconducting materials. As a result, metal oxides have become major prospects to replace a-Si:H with their high-performance electrical characteristics and simplicity of processing, making them valuable switching elements in display technology. Particularly, quaternary metal oxides such as the amorphous Indium-Gallium-Zinc-Oxide (IGZO) have demonstrated extremely high performances as TFTs, prompting extensive research in the field.

The conventional method of producing metal oxide thin films has been through vacuum deposition methods such as sputtering. However, for large area applications these vacuum deposition methods face inherent limitations which prevent easy application and device fabrication. Facing these restrictions, solution-processing has become a popularly researched alternative in producing metal oxide thin films due to their simple processing requirements, low cost, and ability to be applied over large areas. In solution-processed IGZO, there have been a couple approaches to improve device performance and stability as well as simplify processing. In this work, we produce a gallium-rich 2:2:1 IGZO TFT using solution processes and study its electrical characteristics and stability. In this paper, we demonstrate a working solution-processed gallium-rich 2:2:1 IGZO TFT and compare it to a solution-processed indium-rich device to quantify its stability and performance. Through this work, we show that solution-processing is a viable fabrication method for gallium-rich IGZO, which can be a high-stability alternative to other compositions of IGZO devices.