  Epitaxial growth of \k{appa}-phase Ga2O3 thin films are investigated on
c-plane sapphire, GaN- and AlNon-sapphire, and (100) oriented yttria stabilized
zirconia (YSZ) substrates via metalorganic chemical vapor deposition (MOCVD).
The structural and surface morphological properties are investigated by
comprehensive material characterization. Phase pure \k{appa}-Ga2O3 films are
successfully grown on GaN-, AlN-on sapphire, and YSZ substrates through a
systematical tuning of the growth parameters including the precursor molar flow
rates, chamber pressure and growth temperature, whereas the growth on
c-sapphire substrates leads to a mixture of \b{eta}- and \k{appa}polymorphs of
Ga2O3 under the investigated growth conditions. The influence of the
crystalline structure, surface morphology and roughness of \k{appa}-Ga2O3 films
grown on different substrates are investigated as a function of precursor flow
rate. High resolution scanning transmission electron microscopy (HR-STEM)
imaging of \k{appa}-Ga2O3 films reveals abrupt interfaces between the epitaxial
film and the sapphire, GaN and YSZ substrates. The growth of single crystal
orthorhombic \k{appa}Ga2O3 films is confirmed by analyzing the STEM
nano-diffraction pattern. The chemical composition, surface stoichiometry, and
the bandgap energies of \k{appa}-Ga2O3 thin films grown on different substrates
are studied by high resolution x-ray photoelectron spectroscopy (XPS)
measurements. The type-II (staggered) band alignments at three interfaces
between \k{appa}-Ga2O3 and c-sapphire, AlN, and YSZ substrates are determined
by XPS, with the exception of \k{appa}-Ga2O3/GaN interface, which shows type I
(straddling) band alignment.
