Epitaxial growth of δ-Ga${}_2$O${}_3$ Thin films grown on YSZ and sapphire substrates using β-Fe${}_2$O${}_3$ buffer layers via mist chemical vapor deposition

Herein, epitaxial δ-Ga${}_2$O${}_3$ thin films are successfully grown on various planes of yttria-stabilized zirconia (YSZ) and c-plane sapphire substrates by inserting the same crystal-structured β-Fe${}_2$O${}_3$ and bcc-In${}_2$O${}_3$ buffer layers via mist chemical vapor deposition. X-ray diffraction (XRD) measurements reveal that various planes of δ-Ga${}_2$O${}_3$ thin films are grown in both the out-of-plane and in-plane orientations using the same crystal-structured buffer layers to reduce the lattice mismatch. δ-Ga${}_2$O${}_3$ (111) is demonstrated to grow on the YSZ (111) in the narrow growth temperature range of 575-675 °C due to thermal instability of β-Fe${}_2$O${}_3$ buffer layers. Next, a c-plane sapphire wafer as a substrate using two buffer layers for the growth of δ-Ga${}_2$O${}_3$ is investigated. XRD 2θ–ω scan reveals that the mixture of α- and δ-Ga${}_2$O${}_3$ thin films is grown on Fe${}_2$O${}_3$/In${}_2$O${}_3$/c-plane sapphire. This is because the Fe${}_2$O${}_3$ buffer layers are phase separated into α and β phases due to the large grain size of the In${}_2$O${}_3$ buffer layer. XRD φ-scan profiles indicate that the δ-Ga${}_2$O${}_3$ thin film grown on sapphire is composed of a twin domain. This study contributes to our understanding of the growth mechanism of δ-Ga${}_2$O${}_3$ and its future applications in devices. (© 2023 Wiley‐VCH GmbH)