The dependence of the conductivity of the films of hafnium oxide HfO_2 synthesized in different modes is studied. Depending on the modes of synthesis, the conductivity of HfO_2 at a fixed electric field of 1.0 MV/cm changes by four orders of magnitude. It is found that the conductivity of HfO_2 is limited by the model of phonon-assisted tunneling between the traps. The thermal and optical energies of the traps W _t = 1.25 eV and W _opt = 2.5 eV, respectively, in HfO_2 are determined. It is found that the exponentially strong scattering of the conductivity of HfO_2 is due to the change in the trap density in a range of 4 × 10^19–2.5 × 10^22 cm^–3. In the cathodoluminescence spectra of HfO_2, a blue band with the energy of 2.7 eV is observed which is due to the oxygen vacancies. A correlation between the trap density and intensity of cathodoluminescence, as well as between the trap density and refractive index, is found. A nondestructive in situ method for the determination of the trap density of hafnium oxide with the use of the measurement of the refractive index is proposed. The optimum values of the concentrations of oxygen vacancies for emitting devices on the basis of the films of HfO_2 are found.
Using the methods of low-temperature luminescence spectroscopy and vacuum ultraviolet synchrotron radiation (MAX IV synchrotron, Lund, Sweden), charge transfer processes and the nature of charge carrier traps responsible for leakage currents in nanometer dielectric films of hafnium-zirconium-oxygen solid solutions on silicon substrate, as well as in films doped with La-ions and annealed in argon atmosphere. The photoluminescence spectra, photoluminescence excitation spectra of the 2.7 eV emission band and previous simulation data within the framework of density functional theory confirm the presence of an oxygen vacancy in the studied films. Based on the study of competing channels for the relaxation of electronic excitations due to the radiative decay of self-trapped excitons (4.35 eV emission band) and the luminescence of defects (2.7 and 3.5 eV emission bands), a conclusion was made about the efficiency of transport and capture of excitons and separate charge carriers in films with varying degrees of defectiveness and films doped with lanthanum. The obtained data confirm the conclusion that oxygen vacancies are traps responsible for leakage currents in the films under study.
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