Influence of Annealing on the 1.5 μm Light Emission of Er-doped ZnO Thin Films and its Crystal Quality

Intensity variation of 1.5 μm light emission at room temperature from Er-doped epitaxial and polycrystal ZnO films depending on annealing temperature (773–1373 K) was studied. As-grown Er-doped epitaxial ZnO film emitted 1.5 μm photoluminescence(PL) higher than as-grown Er-doped polycrystal ZnO. It was found that the annealing in air increases PL intensity and the maximum PL intensity was obtained by annealing at optimal temperature (1073 K). Spectrum shape and intensity of 1.5 μm PL of Er-doped epitaxial ZnO after annealing at 1073 K resembled those of Er-doped polycrystal ZnO after annealing at 1073 K. X-ray diffraction measurement demonstrated that annealing improves crystal quality of Er-doped ZnO film. We assumed that the process of 1.5 μm light emission is dependent on local area placement of Zn and O atoms around Er as well as crystal quality of ZnO.