Study on the Effect of Annealing on Ga${}_2$O${}_3$ Thin Films Deposited on Silicon by RF Sputtering

Gallium oxide is an ultra-wide bandgap semiconductor with excellent opto-electronic properties, making it a highly promising material for a wide range of applications and devices. In this article, we report how the optical, morphological, structural, and compositional properties of $\beta$-Ga${}_2$O${}_3$ thin films deposited by RF sputtering on silicon substrates are affected by thermal treatments. Ellipsometric spectra recorded at multiple angles of incidence from several samples subjected to thermal annealing in the range of 550-1000 ${}^{\circ }$C were analyzed to extract the optical functions using appropriate multilayer models. This analysis is complemented by compositional, structural, and morphological characterization techniques. A significant increase of the refractive index was found after annealing at 1000 ${}^{\circ }$C, accompanied by a stark improvement in the samples’ crystalline structure, as confirmed by complementary structural and compositional characterization techniques.