X-ray absorption spectroscopy and Eu 3+ -emission characteristics in GaAs/SnO 2 heterostructure

X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) data are used for investigating heterostructure samples of GaAs/SnO 2 . XANES data are used for analyzing the local organization around Eu in the heterostructure formed by GaAs and Eu-doped SnO 2 . The differences between the XANES data for these samples and data obtained for Eu-doped SnO 2 thin films, deposited on glass substrate, are assumed as responsible for the differences in the photoluminescence (PL) spectra concerning the Eu 3+ emission, since films deposited on glass substrate do not present Eu 3+ PL transitions until the annealing temperature is rather high. Eu 3+ emission is explored using two different excitation sources: 350 nm from a Kr + laser (above SnO 2 energy bandgap) and 488 nm from an Ar + laser (below SnO 2 bandgap energy). The existence of more organized regions around the Eu 3+ site observed for the heterostructure surface may be associated with the Eu 3+ luminescent emission. The main and secondary features in the XANES show that there are differences in the average local Eu environment for the SnO 2 :Eu isolated thin films and heterostructures, being more organized in the latter. Electrical characterization evidences that the portion of the resistivity reduction that corresponds to photo-ionized intrabandgap states is responsible for the persistent photoconductivity phenomenon in the heterostructures.