  Phase pure \b{eta}-(AlxGa1-x)2O3 thin films are grown on (001) oriented
\b{eta}-Ga2O3 substrates via metalorganic chemical vapor deposition (MOCVD). By
systematically tuning the precursor molar flow rates, the epitaxial growth of
coherently strained \b{eta}-(AlxGa1-x)2O3 films are demonstrated with up to 25%
Al compositions as evaluated by high resolution x-ray diffraction (XRD). The
asymmetrical reciprocal space mapping confirms the growth of coherent
\b{eta}-(AlxGa1-x)2O3 films (x < 25%) on (001) \b{eta}-Ga2O3 substrates. While
the films show smooth surface morphologies, the alloy inhomogeneity with local
segregation of Al along (-201) plane is observed from atomic resolution STEM
imaging, resulting in wavy and inhomogeneous interfaces in
\b{eta}-(AlxGa1-x)2O3/\b{eta}-Ga2O3 superlattice structure. Room temperature
Raman spectra of \b{eta}-(AlxGa1-x)2O3 films show similar characteristics peaks
as (001) \b{eta}-Ga2O3 substrate without obvious Raman shifts for films with
different Al compositions. Atom probe tomography (APT) was used to investigate
the atomic level structural chemistry with increasing Al content in the
\b{eta}-(AlxGa1-x)2O3 films. A monotonous increase in chemical heterogeneity is
observed from the in-plane Al/Ga distributions which was further confirmed via
statistical frequency distribution analysis (FDA). Although the films exhibit
alloy fluctuations, n-type doping with good electrical properties are
demonstrated for films with various Al compositions. The determined valence and
conduction band offsets at \b{eta}-(AlxGa1-x)2O3/\b{eta}-Ga2O3 heterojunctions
using x-ray photoelectron spectroscopy (XPS) reveal the formation of type-II
(staggered) band alignment.
