Effects of Al-Doping Concentration on the Photoresponse Properties of Al-Doped ZnO Thin Films with ZnO Buffer Layer

We prepared Al-doped ZnO (AZO) thin films with Al doping concentrations of 0, 1, 2, and 3 at.% by a sol gel spin-coating method onto an oxidized Zn buffer layer. The structural properties and morphology were investigated by X-ray diffraction (XRD) and field-emission scanning electron microscopy (FE-SEM). The full width at half maximum of the XRD peaks for the ZnO (002) plane increased with increasing Al content, which corresponded to a decreased grain size of the films in the SEM images. In the photoluminescence spectra, the near-band edge and deep-level emissions also decreased with an increase in the Al-doping concentration. All of the Al-doped ZnO thin films showed higher dark and photocurrents in comparison to the non-doped ZnO thin film in a linear current voltage curve, and the 1 at.% Al-doped ZnO thin film had the highest mobility and lowest resistivity, which led to the best responsivity for use in a UV detector.