Growth, catalysis and faceting of $α$-Ga$_2$O$_3$ and $α$-(In$_x$Ga$_{1-x}$)$_2$O$_3$ on $m$-plane $α$-Al$_2$O$_3$ by molecular beam epitaxy

Martin S. Williams; Manuel Alonso-Orts; Marco Schowalter; Alexander Karg; Sushma Raghuvansy; Jon P. McCandless; Debdeep Jena; Andreas Rosenauer; Martin Eickhoff; Patrick Vogt

doi:10.1063/5.0180041

paper

Growth, catalysis and faceting of $α$ -Ga $_{2}$ O $_{3}$ and $α$ -(In $_{x}$ Ga $_{1 - x}$ ) $_{2}$ O $_{3}$ on $m$ -plane $α$ -Al $_{2}$ O $_{3}$ by molecular beam epitaxy

arXiv:2311.12460 · doi:10.1063/5.0180041

Abstract

The growth of $α$ -Ga $_{2}$ O $_{3}$ and $α$ -(In $_{x}$ Ga $_{1 - x}$ ) $_{2}$ O $_{3}$ on $m$ -plane $α$ -Al $_{2}$ O $_{3}$ (10 $1 ˉ$ 0) by molecular beam epitaxy (MBE) and metal-oxide-catalyzed epitaxy (MOCATAXY) is investigated. By systematically exploring the parameter space accessed by MBE and MOCATAXY, phase-pure $α$ -Ga $_{2}$ O $_{3}$ (10 $1 ˉ$ 0) and $α$ -(In $_{x}$ Ga $_{1 - x}$ ) $_{2}$ O $_{3}$ (10 $1 ˉ$ 0) thin films are realized. The presence of In on the $α$ -Ga $_{2}$ O $_{3}$ growth surface remarkably expands its growth window far into the metal-rich flux regime and to higher growth temperatures. With increasing O-to-Ga flux ratio ( $R_{O}$ ), In incorporates into $α$ -(In $_{x}$ Ga $_{1 - x}$ ) $_{2}$ O $_{3}$ up to $x \leq 0.08$ . Upon a critical thickness, $β$ -(In $_{x}$ Ga $_{1 - x}$ ) $_{2}$ O $_{3}$ nucleates and subsequently heteroepitaxially grows on top of $α$ -(In $_{x}$ Ga $_{1 - x}$ ) $_{2}$ O $_{3}$ facets. Metal-rich MOCATAXY growth conditions, where $α$ -Ga $_{2}$ O $_{3}$ would not conventionally stabilize, lead to single-crystalline $α$ -Ga $_{2}$ O $_{3}$ with negligible In incorporation and improved surface morphology. Higher $T_{G}$ further results in single-crystalline $α$ -Ga $_{2}$ O $_{3}$ with well-defined terraces and step edges at their surfaces. For $R_{O} \leq 0.53$ , In acts as a surfactant on the $α$ -Ga $_{2}$ O $_{3}$ growth surface by favoring step edges, while for $R_{O} \geq 0.8$ , In incorporates and leads to a-plane $α$ -(In $_{x}$ Ga $_{1 - x}$ ) $_{2}$ O $_{3}$ faceting and the subsequent ( $2 ˉ$ 01) $β$ -(In $_{x}$ Ga $_{1 - x}$ ) $_{2}$ O $_{3}$ growth on top. Thin film analysis by STEM reveals highly crystalline $α$ -Ga $_{2}$ O $_{3}$ layers and interfaces. We provide a phase diagram to guide the MBE and MOCATAXY growth of single-crystalline $α$ -Ga $_{2}$ O $_{3}$ on $α$ -Al $_{2}$ O $_{3}$ (10 $1 ˉ$ 0).

Growth, catalysis and faceting of α-Ga2​O3​ and α-(Inx​Ga1−x​)2​O3​ on m-plane α-Al2​O3​ by molecular beam epitaxy

Abstract

References in corpus (2)

Growth, catalysis and faceting of $α$ -Ga $_{2}$ O $_{3}$ and $α$ -(In $_{x}$ Ga $_{1 - x}$ ) $_{2}$ O $_{3}$ on $m$ -plane $α$ -Al $_{2}$ O $_{3}$ by molecular beam epitaxy