ZnO is a direct and wide-band gap semiconductor with WZ crystal structure. It has recently attracted considerable attention due to its favorable properties such as the wider band gap (3.37 eV) at room temperature

the large binding energy of excitons (60 meV) at room temperature

and highly c-axis oriented. ZnO has so good photoelectric and piezoelectric properties that it has immensity space for developing at surface (acoustic) wave devices

light emitting diodes (LEDs)

photodetectors

gas sensor and solar cells etc. A variety of deposition techniques have been employed to prepare ZnO thin films

such as pulsed laser deposition (PLD)

molecule beam epitaxy (MBE) and metal-organic chemical vapor deposition (MOCVD). Among them

MOCVD provides the advantages of large-area deposition and high throughput due to higher growth rates. Consequently

MOCVD was adopted to grow ZnO thin films. High-quality ZnO thin films were grown on sapphire (0001) substrates at 590℃ for 20 min by metal-organic chemical vapor deposition (MOCVD). The effect of annealing under different condition on crystal structure and optical properties of ZnO thin films have been studied.The results show that the crystal quality of the films grown on c-plane has been improved largely. Especially the film annealed in oxygen

the XRD peak of ZnO (002) became stronger greatly and the FWHM of XRD peak is only 0.11°. The PL spectra show that the deep energy level emitting disappears in the sample annealed in nitrogen. On the contrary

the deep energy level emitting became stronger for the sample annealed in oxygen. The results show that the deep energy level emitting intensity is related to the concentration of V

Zn

and O

Zn

defects. Additionally

the resistivity of ZnO thin films annealed in oxygen could increase remarkably for the change of the rate of Zn and O. It was an effective method to achieve the high-quality ZnO films

high-resistance ZnO films

even p-type ZnO by annealing under proper condition from our results.