Quantitative subcompound-mediated reaction model for the molecular beam epitaxy of III-VI and IV-VI thin films: Applied to Ga2O3, In2O3, and SnO2

We identify a novel reaction mechanism in the thin film synthesis of compound materials. With the example of the O plasma-assisted molecular beam epitaxy of III-O and IV-O semiconductors-Ga2O3, In2O3, and SnO2-we illustrate this mechanism, involving the intermediate formation of a suboxide. This consecutive reaction mechanism, as well as the competing desorption of a subcompound, are the basis for the development of a quantitative growth model parametrized by three material-dependent parameters. It is proposed and justified to be applicable to other III-VI and IV-VI compounds whose constituents exhibit analogous kinetic and thermodynamic properties to those discussed for oxides. We validate this model quantitatively by experimental growth rate and desorption data as a function of all growth parameters for Ga2O3, In2O3, and SnO2. As the first of its kind, our model serves as a basis for more sophisticated growth models, e.g., describing multicomponent materials or including surface diffusion processes, and can be transferred to other growth techniques and thin films that grow via intermediate reaction products.