Structural, morphological, and optical properties of (${\mathrm{In}}_{1-x}{\mathrm{Ga}}_x{)}_2{\mathrm{O}}_3$ thin films are reported as a function of the cation composition. A material library with $0.1\le x\le 0.64$ was fabricated by discrete combinatorial synthesis on $r$-plane sapphire substrates using pulsed laser deposition. The samples crystallize in the cubic bixbyite phase for $x\le 0.35$. The lattice constant and absorption edge energy systematically decrease and increase, respectively, with increasing Ga content up to $x=0.2$. For higher Ga admixtures, both saturate. In addition, a significant change in surface morphology occurs at $x\sim 0.2$. Transmission electron microscopy examinations of selected samples show a homogeneous incorporation of ${\mathrm{Ga}}_2{\mathrm{O}}_3$ into cubic ${\mathrm{In}}_2{\mathrm{O}}_3$ for $x=0.11$, while a segregation of Ga-rich and In-rich regions can be seen for $x=0.22$ and $x=0.35$. In the sample with $x=0.35$, the Ga-rich regions exhibit a preferred orientation with an angle of ${45}^{\circ }$–${55}^{\circ }$ with respect to the substrate normal, which has been shown to result from a correspondingly faceted In-rich bixbyite layer at the substrate–thin film interface.

• Received 17 May 2023
• Revised 29 August 2023
• Accepted 30 August 2023

DOI:https://doi.org/10.1103/PhysRevMaterials.7.094603