Effects of Aluminium Doping and Electrode Distance on the Performance of Aligned Zinc Oxide Nanorod Array-Based Ultraviolet Photoconductive Sensors

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Metal--semiconductor--metal (MSM) ultraviolet (UV) photoconductive sensors were fabricated using undoped and aluminium (Al)-doped zinc oxide (ZnO) nanorod arrays prepared via the sonicated sol--gel immersion method. Notably, the nanorod diameter decreased with Al-doping, varying in the size range of 30 to 70 nm, compared with undoped ZnO, which had a size range of 80--120 nm. The Al-doped nanorod arrays exhibited optical properties superior to those of the undoped ZnO, with an average transmittance of 85% in the visible region; the Al-doped arrays also showed good UV absorption properties. Photoluminescence measurements indicate that the suppression of defects was observed for the Al-doped ZnO nanorod, as shown by a bigger I_{\text{UV}}/I_{\text{vis}} of 1.24 compared to that of undoped ZnO (0.97). According to the experimental results, the UV responsivity was significantly improved by the Al-doping, with the highest value of 373 A/W obtained at an inter-electrode distance of 0.07 mm under UV light (365 nm, 750 μW/cm2) with a 10 V bias. In addition, the responsivity of the UV sensor also significantly improved when the inter-electrode distances were reduced from 2.00 to 0.07 mm.
2012-06-25