Kinetics, thermodynamics, and catalysis of the cation incorporation into GeO$_2$, SnO$_2$, and (Sn$_x$Ge$_{1-x}$)O$_2$ during suboxide molecular beam epitaxy
Rutile GeO$_2$ is a promising ultra-wide bandgap semiconductor for future power electronic devices whose alloy with the wide bandgap semiconductor rutile-SnO$_2$ enables bandgap engineering and the formation of heterostructure devices. The (Sn$_x$Ge$_{1-x}$)O$_2$ alloy system is in its infancy and m...
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Main Authors | , , , , , |
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Format | Journal Article |
Language | English |
Published |
18.10.2024
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Subjects | |
Online Access | Get full text |
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Summary: | Rutile GeO$_2$ is a promising ultra-wide bandgap semiconductor for future
power electronic devices whose alloy with the wide bandgap semiconductor
rutile-SnO$_2$ enables bandgap engineering and the formation of heterostructure
devices. The (Sn$_x$Ge$_{1-x}$)O$_2$ alloy system is in its infancy and
molecular beam epitaxy (MBE) is a well-suited technique for its thin-film
growth, yet presents challenges in controlling the alloy composition and growth
rate. To understand and mitigate this challenge, the present study
comprehensively investigates the kinetics and thermodynamics of suboxide
incorporation into GeO$_2$, SnO$_2$, and (Sn$_x$Ge$_{1-x}$)O$_2$ during
suboxide MBE, the latest development in oxide MBE using suboxide sources. We
find suboxide MBE to simplify the growth kinetics, offering better control over
growth rates than conventional MBE but without supporting cation-driven oxide
layer etching. During binary growth, SnO incorporation is kinetically favored
due to its higher oxidation efficiency and lower vapor pressure compared to
those of GeO. In (Sn$_x$Ge$_{1-x}$)O$_2$ growth, however, the GeO incorporation
is preferred and the SnO incorporation is suppressed, indicating a catalytic
effect, where SnO promotes GeO incorporation through cation exchange. The
origin of this cation exchange is likely thermodynamic yet calls for further
theoretical studies. Our experimental study provides guidance for controlling
the growth rate and alloy composition of (Sn$_x$Ge$_{1-x}$)O$_2$ in suboxide
MBE, highlighting the impact of the substrate temperature and active oxygen
flux besides that of the mere SnO:GeO flux stoichiometry. The results are
likely transferable to further physical and chemical vapor deposition methods,
such as conventional and hybrid MBE, pulsed laser deposition, mist- or
metalorganic chemical vapor deposition. |
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DOI: | 10.48550/arxiv.2410.14527 |