Extending the Kinetic and Thermodynamic Limits of Molecular-Beam Epitaxy Utilizing Suboxide Sources or Metal-Oxide-Catalyzed Epitaxy
Patrick Vogt, Felix V. E. Hensling, Kathy Azizie, Jonathan P. McCandless, Jisung Park, Kursti DeLello, David A. Muller, Huili Grace Xing, Debdeep Jena, Darrell G. Schlom
Abstract
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.