| ZnO, a wide direct-gap semiconductor, attracts as much attention as GaN inoptoelectronics research field. Its optoelectronic characteristics are little affected byvacancies. And it has great uses in this information age. It can be used to fabricatedisplay devices, high frequency filters, emitting diode, lasers, high speed opticalswitch and so forth. Therefore, it has great uses in both civil and military fields.Atpresent, the research of ZnO is mainly about the growth of material films. A lot ofmethods have been used to deposit ZnO films such as Molecule Beam Epitaxy (MBE),Metal-organic Chemical Vapor Deposition (MOCVD), Pulsed Laser Deposition(PLD), Atomic Layer Epitaxy (ALE), Sputter and Thermal Evaporation. In this thesis,we grew high quality ZnO films by plasma-assisted MOCVD system on c-Al2O3substrate and studied their related characteristics. Meanwhile, based on highresistance ZnO films grown by MOCVD, we successfully designed and fabricatedZnO ultraviolet photodetector. Then characterization and analysis were performed. We grew high quality ZnO films by MOCVD on c-Al2O3 substrate andinvestigated the characteristics of them. X-ray Diffraction (XRD) shows that ZnOfilms are highly c-oriented and the full width at half maximum (FWHM) of (0 0 2)ZnO is 0.28°. Related analysis indicated that a tensile strain was formed in thedeposition process of ZnO. In room temperature Photoluminescence (PL) Spectra, weobserved high-intensity ultraviolet luminescence. The ratio of ultraviolet luminescenceintensity and green luminescence intensity is 14:1 and the forbidden band widthderived from PL spectrum is about 3.31 eV, which indicated good optical quality of 95ZnO films. We compared ZnO films grown on c-Al2O3 in different conditions. Firstly, weoptimized the growth temperature. Results and analyses show that ZnO thin filmgrown with the temperature of 540°C has the best crystal quality and optical quality. We systemically studied the effect of the temperature of DEZn source on thequality of ZnO films grown by MOCVD. XRD spectra show that the change of DEZnsource temperature little effects lattice constant of ZnO, which also means that thetemperature change of DEZn source has little influence on the built-in tensile strain inZnO. ZnO film grown with the temperature of — 19°C had the best crystal quality.Atomic Force Microscopy measurements show that ZnO grown at — 19°C had thesmallest roughness. PL spectra show that the ultraviolet luminescence energy ofsamples decreased with the decrease of DEZn source temperature and increased after—21°C. Considering in lattice-mismatched epitaxial growth, ZnO thin film has atensile built-in strain, so this shift of band gap energy is related to the structurecharacteristic of ZnO films (tensile built-in strain in films). Therefore, the decrease ofultraviolet luminescence energy means that the decrease of tensile strain in ZnO.Results show that tensile built-in strain of ZnO is the smallest when DEZn temperatureis about — 19°C~21°C and has little fluctuation. This indicates that in some range thechange of DEZn temperature has little effect on tensile strain in ZnO films. This resultis in accordance with the analysis of XRD. Sample grown at — 19°C has the highestratio of ultraviolet luminescence intensity and green luminescence intensity, whichshows the best optical quality. Synthetically, ZnO films grown with the temperatureof — 19°C has the best quality. Post-thermal annealing, as one common means to improve films' quality, at high96temperature can make ZnO bonds undergo a relaxation process to cause networkreconstruction. So we investigated the influence of post-thermal annealing on ZnOfilms.1. XRD show that annealing effectively improved the quality of ZnO films andannealing in different ambient didn't introduce ZnO with other directions except for(002). Af...
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