Growth And Properties Study Of ZnO Thin Films Grown By Atmospheric Pressure MOCVD

In this dissertation, the growth and properties of ZnO films grown by a home-made atmosphere pressure MOCVD system(AP-MOCVD) were analysised by X-ray diffraction (XRD), Optical Microscope(OM), Atom Force Microscope(AFM), Photoluminescence Spectrum(PL) and other techniques. Main body of the dissertation is mostly composed of two parts: 1. The determination of the misorientation angle between the ZnO epilayer and Sapphire substrate, the accurate lattice constants of ZnO films, the bending radius of the wafers and stress of ZnO films; 2. The growth and properties analyses of ZnO films grown on Si(111) substrate with an A1N buffer layer by AP-MOCVD. Some main conclusions and new results were obtained as follows:First part: The misorientation and bending of ZnO films on Sapphire by X-ray double crystal diffractometry study.1, Single crystal ZnO films were grown on Al₂O₃ (0001) substrate having a 0.2° miscut angle by AP-MOCVD. The measuring method of the accurate crystal constants was discussed basing on the substrate peak of the X-ray double crystal diffraction spectrum and the errors induced by misorientation must be deducted. 2, The wafer bending were induced because of the lattice and thermal mismatch, which would make the XRD omega rocking curve peak move, so, the bending radius of the wafer can be determinated by XRD and the stress of the films can be calculated. 3, The measured a lattice constant is less than that of body single crystal ZnO and c is larger, which indicates that the films are under the compressive stress. This compressive stress is derived from the lattice and thermal mismatch. 4, Misorientation was exactly assuredly came into being between the ZnO epilayer and Sapphire substrate by X-ray double crystal diffraction measurement. The misorientation azimuth angle is nearly same with the miscut azimuth of sapphire substrate, which indicates that substrate miscut is one of the key factors of the misorientation, but, the misoriention angle is greatly little comparing with the substrate miscut angle 0.2° . the sample with a low-temperature buffer layer has a misorientation angle of 0.019° and that of direct growth is 0.023 ° . 5, The bending radius of the directly growing wafer is 26.86m and the stress in that film is 0.42GPa and that of wafer with a LT buffer are 37.76m and 0.36GPa, respectively. All results show that the low-temperature buffer layer is of great benefit to reduce the misoriention and lattice distortion of ZnO films on Al₂O₃ and enhance the quality of ZnO films.Second part: The Growth and Property of ZnO Film on Si(111) Substrate with A1NBuffer by MOCVD.1> ZnO films were grown on Si(lll) substrate by AP-MOCVD system. In order to eliminate the effect on the quality of ZnO from the mismatch and protect the Si substrate from oxidation, an 20nm AIN buffer layer was put forward to grow on substate by low-pressure MOCVD system firstly. Then, the A1N/Si(lll) template was transferred to grow ZnO epilayer in AP-MOCVD system.2^ The lattice constant c of ZnO epilayer and AIN buffer layer was tested and calculated from the space between the XRD (0002) peak and (004) peak. The results are: Czno=0.5195nm and Q/A/=0.4862nm. Both of the figures are little comparing with the body monocrystal standard c lattice constant of ZnO and AIN, which indicates that film are under the compressive stress operation derived from the lattice and thermal mismatch.3^ The Full Wide of Half Maximum(FWHM) of ZnO(0002) plane DCXRD omega rocking curve is 460", which is much less than that minimal value 720" having beenreported and that of ZnO(1012) plane is 1105". This is the first time report of ZnOfilm on Si substrate having the asymmetry plane XRD rocking curve result. 4> The regular oscillation curve was appeared from the laser in-situ interference system, which is a evidence of quasi-two-dimension growth mode during the ZnO film expiation. The growth rate was 4.14um/h from the interference curve. High growth rate is greatly in favor of the future industrialization of ZnO semiconductor film. The crack density Of ZnO surface is 20strip/cm by interfernce microscopy graph determination5^ Only the near band edge emission was appeared in the room temperature photoluminescence(PL) spectrum. Free exciton emission and binding exciton emission accompanied by their LO phonon are also observed from the photoluminescence(PL) spectrum at 10K. All the results indicate that AIN buffer layer is a is a effective route to obtain high quality ZnO film on Si substrate by MOCVD.Dissertation was supported by 863-Project of China with Grant No.2003AA302160 and Electronic Development Foundation in China:...