Growth of lanthanum (La) doped zinc oxide (ZnO) films and investigation of their characterizations

In this study, La-doped Zinc Oxide (Zn:La) films were obtained by chemical Spray pyrolysis on to soda-lime glass and n-Si substrates at various ratios of La (0%, 1%, 2%, 4% and 5% (at.%)) content. For electrical measurements, Au (gold) contacts on ZnO:La films were grown by thermal evaporation method and Schottky type devices (Au / ZnO: La / n-Si / Al) were obtained. Some structural parameters of the films were calculated from XRD (X-ray diffraction) patterns and all films were found to have hexagonal wurtzite crystal structure. The optical properties of ZnO:La films were investigated by UV spectroscopy wavelength range between 350 nm and 800 nm and the films were found to have a band gap between 3.12-3.30 eV. Surface morphologies of films were investigated by AFM (Atomic Force Microscopy) and SEM (Scanning Electron Microscopy) analyzes. Besides, I-V (current-voltage) and C-V (capacitance-voltage) measurements of Schottky diodes were obtained. Characteristic diode parameters such as n (ideality factor) and Φb (barrier height) obtained by I-V measurements of devices were calculated by taking TE (thermionic emission) theory into consideration. Additionally, Φb (barrier height) and Rs (series resistance) values were calculated by Norde function. C-V measurements of La-doped diodes at different ratios were taken at 100, 200, 500 and 1000 kHz frequencies. Basic diode parameters such as barrier height, Ef (fermi energy levels), Nd (carrier concentration) and Vd (diffusion potential) were calculated from 1/C2-V graph. All results were evaluated in detail.