Effect of Ag photodoping on deep-level emission spectra of ZnO epitaxial films

Abstract

Effect of Ag photodoping into ZnO films grown by molecular beam epitaxy has been examined via the real-time measurement of photoluminescence (PL) spectra using a HeCd laser at room temperature. While an asymmetric deep-level (green-yellow) broadband (D) is observed in PL of as-grown ZnO, it appears to change to two distinct bands (at 2.29 and 2.50 eV) in the illuminated Ag/ZnO. From the result of a Gaussian fitting, the yellow band at 2.29 eV is evaluated to relate with photodoped Ag atoms. With increasing the laser illumination time (photodoping), the PL intensity of broadband (I D ) decreases and contrarily, the intensity of the near band edge emission observed at 3.297 eV (I NB ) shows a tendency to increase. We believe that the Ag can be photodoped into ZnO at 300 K and it contributes to the suppression of deep-level band, which results in an increase of I NB .