Structures and Photoluminescence Properties of ZnO Films Epitaxially Grown by Atmospheric Pressure MOCVD

High-quality ZnO () epitaxial films have been grown on sapphire () substrate by atmospheric pressure MOCVD method using zinc acetylacetonate (Zn(C5H7O2)2) and oxygen. The crystallinity of the ZnO films was considerably improved with increasing the film thickness. The full width at half maximum (FWHM) obtained from the ω rocking curve of X-ray diffraction indicated a minimum value of 0.35° at the film thickness of 0.30 μm. The lattice constant estimated from the diffraction angle 2θ was almost equivalent to the value of single crystalline bulk ZnO. The room temperature photoluminescence spectrum of the ZnO films consists of band edge emission at 380.08 nm. The low-temperature (4.2 K) photoluminescence spectrum indicates two broad lines of 3.31 and 3.32 eV from donor–acceptor pairs and one sharp line of 3.363 eV from exciton bound nature donor.