Optimizing Ar:O2 flux ratio for enhanced growth and performance of gallium oxide films on glass substrates and thin film transistors

Abstract

Gallium oxide (Ga₂O₃) is an emerging semiconductor with an ultra-wide band gap of 4.8 eV. However, the preparation and property optimization of Ga₂O₃ thin films still face challenges, especially in terms of cost-effectiveness and process simplicity. This study used RF magnetron sputtering to deposit Ga₂O₃ films on amorphous glass substrates, showcasing excellent performance with the potential to substitute costlier substrates, while extensively examining their structural, optical, and photovoltaic characteristics. The as-grown Ga₂O₃ thin films were in an amorphous state while annealing the films in the air at 600 °C led to the formation of monoclinic structures. A systematic investigation was conducted into the impact of the Ar:O₂ flux ratio on the properties of the films. Annealing amorphous Ga₂O₃ films at 500 °C resulted in an expanded band gap and enhanced transmittance in the ultraviolet range while maintaining the same Ar:O₂ flux ratio. Although crystalline monoclinic Ga₂O₃ and amorphous Ga₂O₃ can be used to fabricate thin-film transistors, amorphous Ga₂O₃ exhibits superior thermal stability and requires a less demanding growth process. A dual-layer structure comprising indium-zinc-oxide and amorphous Ga₂O₃ was utilized as an active layer to thoroughly examine the transmission characteristics of thin-film transistors. Experimental results revealed that these transistors exhibit exceptional electrical characteristics, including a notable switching current ratio of approximately 10⁸, a mobility of 32.3 cm²/Vs, and a subthreshold swing of 0.38 V/dec. These results indicate the feasibility of using Ga₂O₃ thin-film transistors in flat panel displays.