【International Papers】Polarization-dependent resonant inelastic x-ray scattering of β-Ga₂O₃: An experimental and computational study

      Researchers from the Karlsruhe Institute of Technology have published a dissertation titled "Polarization-dependent resonant inelastic x-ray scattering of β-Ga₂O₃: An experimental and computational study" in APL Materials.

Background      

      Ga₂O₃ is an ultra-wide bandgap material, with literature bandgap values ranging from 4.4 to 4.9 eV. It can be used as a transparent conductive oxide (TCO), with good electrical conductivity and transparency in the UV–visible light region. Ga₂O₃ has been used in a wide variety of applications: as a buffer or intrinsically “high-resistive” layer in Cu(In, Ga)Se₂ (CIGSe)- based thin-film solar cells, in power electronics, solar-blind UV detectors, gas-sensing devices, catalysts, and spacebased applications. A detailed and fundamental understanding of its electronic structure is crucial for further insight-driven optimization of these (and similar) devices.

Abstract

      The bulk electronic structure of β-Ga₂O₃ single crystals was investigated using oxygen K-edge x-ray emission and absorption spectroscopy as well as resonant inelastic soft x-ray scattering. Spectra were obtained for different orientations of the crystal planes with respect to the polarization vector of the incident x-ray beam. The spectra are analyzed with calculations based on density functional theory and using the Bethe–Salpeter equation in the ocean code to take the core–hole interaction into account. These calculations correctly capture all the main features in the experimental spectra, demonstrating the potential of the approach to predict the electronic properties of similar compounds. We find a pronounced anisotropy as a function of the excitation polarization vector and significant differences in the spectral contributions from the inequivalent oxygen atoms of β-Ga₂O₃.