The thesis is devoted to experimental investigation and theoretical explanation of optical, luminescence and electrically conductive properties of (Y0,06Ga0,94)2O3 and β–Ga2O3 thin films.
The purpose of this dissertation is to study the optical properties of thin films on the basis of (Y0,06Ga0,94)2O3 and β–Ga2O3, the features of their luminescent characteristics, depending on the conditions of obtaining, the establishment of radiation mechanisms and the study of the characteristics of centers of glow, determination of methods for increasing the electrical conductivity of these films, as a consequence, the creation on this basis of effective luminescent materials for display applications.
The structure of (Y0,06Ga0,94)2O3 and β–Ga2O3 thin films, obtained by high-frequency ion-plasma sputtering, after annealing at different atmosphere was investigated. The spectra of IR reflection of system thin film β–Ga2O3 – fused quartz substrate υ–SiO2 in region 400–1600 cm-1 at 295 K were measured. The peaks in the spectrum of films β–Ga2O3, associated with vibration of Ga – O fragments in structural tetrahedral GaO4 and octahedral GaO6 complexes was interpreted. Light dispersion in (Y0,06Ga0,94)2O3 thin films is studied and parameters of the three-parameter single oscillation model are determined. Fundamental absorption edge of (Y0,06Ga0,94)2O3 thin films was investigated, using the method of optical spectroscopy. It was established that these films are formed in the monoclinic structure of β–Ga2O3. The optical band gap of these films is greater than β–Ga2O3 films and is 4,66 eB for films annealed in oxygen atmosphere, 4,77 eV for the films annealed in argon atmosphere and 4,87 eV for the films, restored in a hydrogen atmosphere. Consolidated effective mass of free charge carriers in (Y0,06Ga0,94)2O3 films after annealing and after reconstitution in hydrogen was estimated. It was found that the concentration of charge carriers after annealing in oxygen atmosphere is 1,32×1018 cm-3, after annealing in argon atmosphere – 3,41×1018 cm-3 and after reconstitution in hydrogen is 5,20×1018 cm-3, which is typical for degenerated semiconductors. It was shown that the shift of fundamental absorption edge in thin films (Y0,06Ga0,94)2O3 is caused by Burstein-Moss effect.
Photoexcitation and photoluminescence spectra of β–Ga2O3 and (Y0,06Ga0,94)2O3 thin films was investigated. Luminescence spectra were factorized on ultimate constituents using Alentsev-Fock method. The nature of two intensive luminescent band with maxima in region 3,00 and 3,15 eV and two faint intensive luminescent band with maxima in region 4,00 and 4,25 eV was discussion. Luminescence decay time for band with maximum in region 3,00 and 3,15 eV in different types of β–Ga2O3 and (Y0,06Ga0,94)2O3 thin films was established. The electrical conductivity of β–Ga2O3 and (Y0,06Ga0,94)2О3 thin films depending on the conditions and atmosphere of thermal treatment were investigated. After annealing in reducing atmosphere of hydrogen obtained a significant decrease in the resistivity of thin films from 10 11 Ohm×cm for films annealed in oxygen or argon to 10 8 Ohms×cm was found. The activation energy of temperature quenching donor centers that is in obtained thin films was determined and the analysis of the results was investigated. Irrespective of the composition of the atmosphere in annealing β–Ga2O3 thin films photoconductivity observed effect it was shown. Compare photoconductivity spectra with the spectra excitations of luminescence indicated that the photoconductivity of β–Ga2O3 thin films associated with band-band transitions with the creation of free charge carriers in the conduction band.
