Figure 4
Normalized XEOL spectra measured at several selected X-ray energies across the Ga K-edge (EK = 10367 eV) at 15 K on a single-crystalline GaN-(0001) thin film grown on crystalline sapphire substrate. The inset schematically illustrates the sample orientation relative to the polarization vector E of the incident X-ray beam and the direction of the collected XEOL signal. Note that the measurement geometry corresponds to the mixed polarization case as the incidence angle of the linearly polarized X-ray beam is 45° with respect to the crystal axis c. The emission bands are labeled based on PL studies (Reshchikov, 2021; Reshchikov et al., 2018), with the definition of the abbreviations given in Section 3.4. |