[TuP3G] Oxide Materials & Devices

[TuP3G-06] Deposition and Annealing Temperature Dependence of the Structural and Optical Properties of Mist-CVD-Grown Gallium Oxide Thin Films on c-plane Sapphire Substrates

〇Masatoshi Koyama¹, Iori Yamasaki¹, Shunsuke Enoki¹, Misaki Nishikawa¹, Kazuto Koike¹, Akihiko Fujii¹, Toshihiko Maemoto¹ (1. Osaka Inst. Tech. (Japan))

Gallium oxide (Ga₂O₃) is a promising material for deep-ultraviolet (DUV) photodetectors. This study investigates the influence of deposition temperature (140–320°C) on the structural and optical properties of Ga₂O₃ thin films synthesized via mist chemical vapor deposition. XRD analysis showed that films deposited at temperatures up to 300°C were amorphous, while crystallization into α-Ga₂O₃ occurred at 320°C. Although all films exhibited high transparency, a subgap absorption feature appeared near 300 nm in the amorphous films, with its intensity depending on the deposition temperature of the films. This absorption likely originates from the tail or subgap states related to structural imperfections and impurities. FTIR spectroscopy revealed that the chemical bonds derived from the Ga(acac)₃ precursor remained in the films deposited at or below 300°C but vanished upon crystallization. The correlation between these residual bonding states and the resulting optical properties, including the effects of annealing, will be discussed.