【International Papers】Composition Analysis of β-(InₓGa₁₋ₓ)₂O₃ Thin Films Coherently Grown on (010) β-Ga₂O₃ via Mist CVD

      Researchers from the Kyoto Institute of Technology have published a dissertation titled "Composition Analysis of β-(In_xGa_1-x)₂O₃Thin Films Coherently Grown on (010) β-Ga₂O₃ via Mist CVD" in Science and Technology of Advanced Materials.

Abstract

      This study investigates the compositional analysis and growth of β-(In_xGa_1-x)₂O₃ thin films on (010) β-Ga₂O₃ substrates using mist chemical vapor deposition (CVD), including the effects of the growth temperature. We investigated the correlation between In composition and b-axis length in coherently grown films, vital for developing high-electron-mobility transistors and other devices based on β-(In_xGa_1-x)₂O₃. Analytical techniques, including X-ray diffraction (XRD), reciprocal space mapping, and atomic force microscopy, were employed to evaluate crystal structure, strain relaxation, and surface morphology. The study identified a linear relationship between In composition and b-axis length in coherently grown films, facilitating accurate composition determination from XRD peak positions. The films demonstrated high surface flatness with root-mean-square roughness below 0.6 nm, though minor relaxation and granular features emerged at higher In compositions (x = 0.083) at the growth temperature of 750°C. XRD results revealed that lattice relaxation were observed at a growth temperature of 700°C despite low In composition. In contrast, at 800°C, the In composition was higher than at 750°C, and coherent growth was achieved. The surface morphology was the flattest at 750°C. These findings indicate that the growth temperature plays a crucial role in the mist CVD growth of β-(In_xGa_1-x)₂O₃ thin films. This study offers insights into the relationship between In composition and lattice parameters in coherently grown β-(In_xGa_1-x)₂O₃ films, as well as the effect of growth conditions, contributing to the advancement of ultra-wide bandgap semiconductor device development.

Figure 1. Relationship between In concentration in the solution and the In composition in the thin film. The dashed line represents the linear approximation.

Figure 2. XRD 2θ-ω patterns for β-(In_xGa_1-x)₂O₃ thin films with varying In compositions.