Reduction in the persistence photoconductivity of spray coated Zn_0.94La_0.06O films: influence of deposition temperature

A detailed investigation of the effect of deposition temperature on the defect-mediated persistence photoconductivity of Zn_0.94La_0.06O films deposited using the spray pyrolysis method reported. The X-ray diffraction peaks corresponding to the wurtzite structure of ZnO with maximum intensity along (1 0 1) plane. The films deposited at 450 ℃ showed increased crystallite size of ~ 24 nm and decreased strain ~ 1.9 × 10^–3 and dislocation density ~ 3.3 × 10¹¹ lines/cm². The scanning electron microscope showed a mixed fibrous morphology for Zn_0.94La_0.06O films deposited 450 ℃. The transparency above 90% in the visible region and increased bandgap of 3.26 eV were observed for the films deposited at 450 ℃. The computation of defects using the area under the curve of photoluminescence spectra revealed an improvement in the crystallinity and a decrease in different defects with the deposition temperature. The films deposited at 450 °C showed a charge carrier density of 8.5 × 10¹⁶ cm⁻³, mobility of 49.6 cm²/Vs, and a lower resistivity of 2.5 × 10² Ω cm. The increment in the photocurrent was noticed in all the films under the illumination of UV light, and the films synthesized at 450 °C showed the highest photocurrent. Due to the existence of Zn and O-related defects that function as a trap centres, the photo resistance remained in all the deposited films. However, the films deposited at 450 °C showed enhanced photo response and photosensitivity due to the improved crystalline quality and lesser defects, which leads to rapid electron–hole recombination. As a result, Zn_0.94La_0.06O films deposited at 450 °C can be used in the fabrication of UV photodetector.