Photoluminescence Properties of Ultra-high-quality ZnO Thin Films Grown by Sputtering Deposition

We have investigated photoluminescence properties of ultra-high quality ZnO thin films grown by an rf-magnetron sputtering method. From the results of x-ray diffraction patterns, we have found that a high growth temperature of ∼600 degree sign C and the introduction of a low-temperature buffer layer are essential in the growth of the high-quality thin films. In photoluminescence (PL) spectra, the free exciton band is observed and the defect-related PL is negligibly weak, reflecting high crystallinity of the film. Furthermore, under high-density excitation conditions, a PL band due to an exciton-exciton scattering process, the so-called P emission, is observed