Abstract
Epitaxial layers of monoclinic β‐Ga~2~O~3~ were successfully grown on (0001) sapphire and ($ \bar 1 $11)~As~ GaAs substrates using metal‐organic vapor‐phase epitaxy (MOVPE). Triethylgallium (TEGa) and N~2~O were used as precursors for gallium and oxygen, respectively. Growth conditions could be determined, where β‐Ga~2~O~3~ grows epitaxially on c ‐plane sapphire and ($ \bar 1 $11)~As~ GaAs substrates. X‐ray diffraction (XRD) and transmission electron microscopy (TEM) measurements identify a epitaxial relationship with ($ \bar 2 $01) β‐Ga~2~O~3~ || (0001) sapphire and ($ \bar 2 $01) β‐Ga~2~O~3~ || ($ \bar 1 $11)~As~ GaAs. The observed sixfold rotational in‐plane symmetry results from differently oriented rotational domains of monoclinic β‐Ga~2~O~3~ with twofold symmetry. Thin films deposited on substrates of other orientation show the formation of the low‐temperature modification α‐Ga~2~O~3~. Optical transmission spectra measured in the spectral range from 200 nm to 2000 nm show a well‐distinct absorption edge at about 5 eV for layers grown on c ‐ and a ‐plane sapphire. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)