Strain status in ZnO film on sapphire substrate with a GaN buffer layer grown by metal-source vapor phase epitaxy

ZnO film of 8@mm thickness was grown on a sapphire (001) substrate with a GaN buffer layer by a novel growth technique called metal-source vapor phase epitaxy (MVPE). The surface of ZnO film measured by scanning electron microscope (SEM) is smooth and shows many regular hexagonal features. The full width at half maximum (FWHM) of ZnO(002) and (102) @w-scan rocking curves are 119 and 202arcsec, corresponding a high crystal quality. The status of the strain in ZnO thick film was particularly analyzed by X-ray diffraction (XRD) @w-2@q scanning. The results show that the strain in ZnO film is compressive, which is also supported by Raman scattering spectroscopy. The compressive strain can solve the cracking problem in the quick growth of ZnO thick film.