| ZnO, as a promising wide band-gap semiconductor (Eg=3.37eV), attracts as much attention as GaN for its potential utilization in short-wavelength light-emitting/detecting devices. In comparison to GaN, its optoelectronic characteristics are little affected by the defects, and it has higher exciton binding energy (60meV at room temperature), lower growth temperature and cost. ZnO materials can be used in many fields, such as display devices, sensors, piezoelectric transducers, transparent conductor, surface acoustic wave devices and lasers operating in the near ultraviolet and blue spectral range. ZnO thin films can be deposited by various methods, such as sputtering, e-beam evaporation, spray pyrolysis, sol-gel, pulsed laser deposition (PLD), metalorganic vapor phase epitaxy (MOVPE), molecular beam epitaxy (MBE), atomic layer epitaxy (ALE), etc. Among these techniques, MOVPE possesses obvious intrinsic advantages, such as selective area growth towards low-dimensional quantum structure, epitaxial lateral overgrowth (ELO) and suitability for growing compound containing volatile elements. It would be especially advantageous for the industrial applications. In this thesis, we prepare ZnO thin films on Al2O3, CaF2 and GaAs substrates by MOVPE and analyze deeply the oriented deviation of growth of the ZnO thin films for the first time. Simultaneously, we investigate thoroughly the influence of the growth temperature and oxygen flow rate on the properties of the films, and the N-doped and intrinsic p-type ZnO thin films are studied systematically.It was found that the growth orientation of the columnar grain in the ZnO films grown on Al2O3 substrates deviated from the c-axis and the growth plane. The deviation was closely related to the substrate temperature. The ZnO films grown at 550癈 had better crystalline quality with smaller orientation deviation, while the films grown at 620 was just on the opposite. The epitaxial relationship between the ZnO films and A12O3 substrate was ZnO (001)//Al2O3(001) , ZnO[100]//Al2O3[110], ZnO[100]//Al2O3[100]. Meanwhile, the growth temperature had quite an effect on the morphology and the opto-electrical properties of the ZnOfilms. The ZnO film grown at 550癈 had larger grain size and smoother surface. But the films with higher optical quality were grown at 600癈 because the deep level emission was barely observed in their photoluminescence (PL) spectra. The intensity ratio of the near-band-edge emission to the deep level emission was as large as 167:1.At the same time, the flow rate of oxygen strongly influenced on the structural and opto-electrical properties of the ZnO thin films on the present growth conditions. Increasing the oxygen flow rate, the crystalline quality of the ZnO thin films was degraded from single-oriented crystal to polycrystalline owning to the formation of O2-induced defects, the averaged grain size became smaller and the root-mean-square roughness decreased. While the optical quality of the films was improved. The intensity ratio of the near-band-edge emission to the deep level emission reached to 148:1 in PL measurements. Thus, the ultraviolet emission in ZnO epilayer might depend strongly on the stoichiometry of the films. Meanwhile, high-O2 content could compensate for the background free-electron concentration generated by native defect of oxygen vacancies, so the electrical resistivity of the ZnO thin films increased with the oxygen flow rate and the electron mobility decreased. The origin of n-type character in un-doped ZnO films was the Vo.NH3-doped ZnO films were grown by plasma-assisted MOVPE. We found that nitrogen could be doped into ZnO films effectively by using plasma generator to realize high-resistivity films. The Zn-N bonds formed in the doped ZnO thin films.High quality ZnO thin film was grown on CaF2 (111) substrate for the first time in china. The film exhibited the preferential (002) orientation with c-axis perpendicular to the surface of the substrate. The full-width at half-maximum (FWHM) of (002) peak in XRD was as narrow as 0.18. At the sam...
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