Extending the Kinetic and Thermodynamic Limits of Molecular-Beam Epitaxy Utilizing Suboxide Sources or Metal-Oxide-Catalyzed Epitaxy

We observe a catalytic mechanism during the growth of III-$\mathrm{O}$ and IV-$\mathrm{O}$ materials by suboxide molecular-beam epitaxy ($S$-MBE). By supplying the molecular catalysts ${\mathrm{In}}_{2}\mathrm{O}$ and SnO we increase the growth rates of ${\mathrm{Ga}}_{2}{\mathrm{O}}_{3}$ and ${\mathrm{In}}_{2}{\mathrm{O}}_{3}$. This catalytic action is explained by a metastable adlayer $A$, which increases the reaction probability of the reactants ${\mathrm{Ga}}_{2}\mathrm{O}$ and ${\mathrm{In}}_{2}\mathrm{O}$ with active atomic oxygen, leading to an increase of the growth rates of ${\mathrm{Ga}}_{2}{\mathrm{O}}_{3}$ and ${\mathrm{In}}_{2}{\mathrm{O}}_{3}$. We derive a model for the growth of binary III-$\mathrm{O}$ and IV-$\mathrm{O}$ materials by $S$-MBE and apply these findings to a generalized catalytic description for metal-oxide-catalyzed epitaxy (MOCATAXY), applicable to elemental and molecular catalysts. We introduce a mathematical description of $S$-MBE and MOCATAXY, providing a computational framework to set growth parameters in previously inaccessible kinetic and thermodynamic growth regimes when using the aforementioned catalysis. Our results indicate that MOCATAXY takes place with a suboxide catalyst rather than with an elemental catalyst. As a result of the growth regimes achieved, we demonstrate a ${\mathrm{Ga}}_{2}{\mathrm{O}}_{3}$/${\mathrm{Al}}_{2}{\mathrm{O}}_{3}$ heterostructure with an unrivaled crystalline quality, paving the way for the preparation of oxide device structures with unprecedented perfection.