Composition analysis of β-(In Ga_1- )₂O₃ thin films coherently grown on (010) β-Ga₂O₃ via mist CVD

This study investigates the compositional analysis and growth of β-(In Ga_1- )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 Ga_1- )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 Ga_1- )₂O₃ thin films. This study offers insights into the relationship between In composition and lattice parameters in coherently grown β-(In Ga_1- )₂O₃ films, as well as the effect of growth conditions, contributing to the advancement of ultra-wide bandgap semiconductor device development.