Controlling the performance of one-dimensional homojunction UV detectors based on ZnO nanoneedles array

Abstract

In this paper, we report on the solution-based synthesis of the n- and p-doped zinc oxide (ZnO) nanoneedle arrays (NNAs) to fabricate p-n homojunction ultraviolet (UV) detectors. Gallium (Ga), copper (Cu), and silver (Ag) were successfully incorporated into the ZnO NNAs lattice by the chemical bath deposition technique. Field emission scanning electron microscope (FESEM) images clearly illustrate the nanoneedles shape for both doped and undoped samples. The growth mechanism of NNAs, together with their structural, morphological, and optical properties, are systematically investigated. Changes of the interplanar spaces in the high-resolution transmission electron microscope (HRTEM) images, peak shifts in the X-ray diffraction (XRD) patterns, and high-resolution X-ray photoelectron spectroscopy (HRXPS) curves all together confirm the successful incorporation of the dopant elements into the ZnO lattice structure. Photocurrent-voltage (I-V) measurements of the one-dimensional p-n homojunction reveal a rectifying diode behavior. Incorporating the Ga donor into the ZnO NNAs decreases the threshold voltage by three times. I-V curves show that the diode with Ag acceptor and Ga donor has the lowest threshold voltage of 0.2 V. These results also manifest that the introduction of Ga donor reduces the rectifying ratio (RR) by five times compared to undoped-ZnO in the diode n-side. The maximum RR of 12.7 is recorded at ±1.5 V for the diode composed of undoped and Cu-doped ZnO. Furthermore, the same diode depicts the UV light highest sensitivity with more than 50 % current enhancement under the UV illumination.