Electronic structure of ß-Ga₂O₃ as seen via measured and calculated resonant inelastic soft x-ray scattering

Transparent conductive oxides (TCOs) are a vital component in a wide variety of technologically important materials such as photovoltaics or light emitting diodes with a rare combination of properties: transparency and electrical conductivity. Improving these materials by reducing absorption while increasing carrier mobility requires an increased understanding of their electronic structure. Resonant inelastic x-ray scattering (RIXS) provides a bulk-sensitive probe of both valence and conduction bands. Here, we demonstrate the suitability of RIXS at the oxygen K edge for examining the electronic structure of TCOs using the example of pristine ß-Ga₂O₃. We compare experimental RIXS maps with those calculated using the Bethe-Salpeter equation (BSE) method within the OCEAN code. We find that the BSE calculations are able to capture all main features of the measured spectra correctly. Controlling the incoming x-ray polarization with respect to the crystallographic axes allows selective excitation of different regions within the band structure, which gives a clear signature in both experimental and theoretical spectra.