Extending the kinetic and thermodynamic limits of molecular-beam epitaxy utilizing suboxide sources or metal-oxide catalyzed epitaxy

TL;DR

This paper reveals a catalytic mechanism in molecular-beam epitaxy using suboxide sources, enabling growth in previously inaccessible regimes and producing high-quality oxide heterostructures.

Contribution

It introduces a generalized model for metal-oxide catalyzed epitaxy (MOCATAXY) and demonstrates enhanced growth rates and material quality using suboxide catalysts.

Findings

Increased growth rates of Ga₂O₃ and In₂O₃ with suboxide catalysts

Development of a computational framework for growth parameter optimization

Production of high-quality Ga₂O₃/Al₂O₃ heterostructures

Abstract

We observe a catalytic mechanism during the growth of III-O and IV-O materials by suboxide molecular-beam epitaxy ($S$-MBE). By supplying the molecular catalysts In$_2$O and SnO we increase the growth rates of Ga$_2$O$_3$ and In$_2$O$_3$. This catalytic action is explained by a metastable adlayer $A$, which increases the reaction probability of the reactants Ga$_2$O and In$_2$O with active atomic oxygen, leading to an increase of the growth rates of Ga$_2$O$_3$ and In$_2$O$_3$. We derive a model for the growth of binary III-O and IV-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 derive 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 MOCATAXY takes place with a suboxide catalyst rather than with an elemental catalyst. As a result of the growth regimes achieved, we demonstrate a Ga$_2$O$_3$/Al$_2$O$_3$ heterostructure with unrivaled crystalline quality, paving the way to the preparation of oxide device structures with unprecedented perfection.