Preparation And Characteristics Of Nonpolar ZnO And ZnMgO Thin Films By MOCVD

Spontaneous polarization and piezoelectric polarization exist in polar ZnO-based heterojunction. As a result, the luminescence efficiency of ZnO-based device would decrease and the luminescent wavelength would redshift. It’s necessary to study on nonpolar ZnO-based materials to eliminate polarization occurs in polar ZnO-based materials. Consequently, the preparation of high crystalline quality nonpolar ZnO-based thin films becomes very important to excellent-performance ZnO-based nonpolar devices.Nonpolar ZnO and ZnMgO thin films were successfully prepared on MgO (100) substrates by MOCVD. Comparing with polar ZnO and ZnMgO thin films, influences of different growth parameters on growth orientation and properties of nonpolar thin films were studied. Up to the present, there’s no report of nonpolar ZnMgO thin films prepared on MgO (100). Hence, the preparation of nonpolar ZnMgO thin film on MgO (100) is meaningful for the progress of nonpolar ZnO-based device.In order to obtain contrast for nonpolar ZnO and ZnMgO thin films, polar ZnO and ZnMgO thin films were prepared on different substrates. Comparing with thin films grown on traditional Si substrates, thin films on MgO (111) substrates had higher intensities, smaller FWHM (Full Width Half Maximum) value and bigger crystal size along c-axis. As a result, ZnO-based thin films grown on MgO (111) substrates had higher crystal quality.Nonpolar ZnO thin films were prepared on MgO (100) substrates. When the flow ratio of Zn precursor and O precursor was 15:30, ZnO thin films showed the strongest nonpolarity. Theory was presented to give an explanation. When nonpolar ZnO was annealed at 800℃, nonpolarity got stronger. However, the optical quality of nonpolar ZnO got decreased.400℃was the optimum growth temperature for nonpolar Zno.97Mg0.030 thin films grown on MgO (100) substrates because the sample grown at 400℃was considered to be m-plane single crystal thin film. The point was, it’s the first time for nonpolar ZnMgO thin film to grow on MgO (100) substrate. The typical morphology for nonpolar ZnMgO thin film was stripe-type structure. When MgO was chosen as a buffer layer, ZnMgO thin film would show more apparent m-plane orientation; when ZnO was chosen as a buffer layer, ZnMgO thin film would have more Mg atoms in it.