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
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| Main Authors: | , , , , , , , , , |
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| Format: | Preprint |
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2023
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| _version_ | 1866910349308985344 |
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| author | Williams, Martin S. Alonso-Orts, Manuel Schowalter, Marco Karg, Alexander Raghuvansy, Sushma McCandless, Jon P. Jena, Debdeep Rosenauer, Andreas Eickhoff, Martin Vogt, Patrick |
| author_facet | Williams, Martin S. Alonso-Orts, Manuel Schowalter, Marco Karg, Alexander Raghuvansy, Sushma McCandless, Jon P. Jena, Debdeep Rosenauer, Andreas Eickhoff, Martin Vogt, Patrick |
| contents | 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$\bar{1}$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$\bar{1}$0) and $α$-(In$_x$Ga$_{1-x}$)$_2$O$_3$(10$\bar{1}$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 ($R_{\text{O}}$), 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 $T_{\text{G}}$ further results in single-crystalline $α$-Ga$_2$O$_3$ with well-defined terraces and step edges at their surfaces. For $R_{\text{O}} \leq 0.53$, In acts as a surfactant on the $α$-Ga$_2$O$_3$ growth surface by favoring step edges, while for $R_{\text{O}} \geq 0.8$, In incorporates and leads to a-plane $α$-(In$_x$Ga$_{1-x}$)$_2$O$_3$ faceting and the subsequent ($\bar{2}$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$\bar{1}$0). |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2311_12460 |
| institution | arXiv |
| publishDate | 2023 |
| record_format | arxiv |
| spellingShingle | 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 Williams, Martin S. Alonso-Orts, Manuel Schowalter, Marco Karg, Alexander Raghuvansy, Sushma McCandless, Jon P. Jena, Debdeep Rosenauer, Andreas Eickhoff, Martin Vogt, Patrick Materials Science 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$\bar{1}$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$\bar{1}$0) and $α$-(In$_x$Ga$_{1-x}$)$_2$O$_3$(10$\bar{1}$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 ($R_{\text{O}}$), 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 $T_{\text{G}}$ further results in single-crystalline $α$-Ga$_2$O$_3$ with well-defined terraces and step edges at their surfaces. For $R_{\text{O}} \leq 0.53$, In acts as a surfactant on the $α$-Ga$_2$O$_3$ growth surface by favoring step edges, while for $R_{\text{O}} \geq 0.8$, In incorporates and leads to a-plane $α$-(In$_x$Ga$_{1-x}$)$_2$O$_3$ faceting and the subsequent ($\bar{2}$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$\bar{1}$0). |
| title | 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 |
| topic | Materials Science |
| url | https://arxiv.org/abs/2311.12460 |