ZnO Nanorod Based Ultraviolet Photodetector Prepared on Patterned Sapphire Substrates
A patterned sapphire substrate with a submicron hole array structure was used to fabricate ZnO nanorod (NR) array by low temperature hydrothermal method. A ZnO seed layer was spin coated using sol gel process and then etched to form separated seed islands. Different concentrations of zinc acetate in the hydrothermal solution were performed for ZnO NR synthesis to investigate ultraviolet (UV) photo response properties. The ZnO NRs synthesized on the patterned substrates were oriented at various inclined angles. The diameter of the NRs increased and their surface to volume ratio decreased as the concentrations of zinc acetate increased from 0.01 to 0.04 M. X ray diffraction and photoluminescence analyses showed that the NRs synthesized at a higher zinc acetate concentration had better crystal quality and fewer defects. The current voltage characteristics of the ZnO NR based metal semiconductor metal photodetectors exhibited a linear relationship, suggesting an Ohmic contact between NRs and Al electrodes. The UV response, defined by the resistance ratio (Rdark/RUV) of the photodetectors increased with the decreasing zinc acetate concentration from 0.04 to 0.01 M. Compared to traditional vertically aligned NR array on plain substrates, the proposed ZnO NR based photodetector on the patterned substrates achieved improved UV responses, and the average increment for samples of 0.01 0.04 M was 145%
IEEE Journal of Selected Topics in Quantum Electronics