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Ultra-violet (UV) radiation harms humans and has a chronic effect on the skin and eyes. This article presents a metal-free, highly transparent zinc oxide-based ultraviolet sensor. To avoid the interface mismatch, gallium-doped zinc oxide (GZO) is used as the top electrode which has very low resistivity to play the role of the transparent interdigital electrode on top of the device to maintain the transmittance. The GZO/ZnO photoconductor configuration is prepared by sputtering the films at room temperature on the glass substrate. For the material and device properties, X-ray diffraction, ultraviolet-visible spectroscopy, scanning electron microscope, and semiconductor parameter analyzer are used. The high visible transmittance is over 85%, with excellent sensitivity under the ultra-violet light density of 4 mW/cm 2 with a wavelength of 365nm. The device performance is not only based on the photoconductive effect but also the pyro-photonic effect of reducing the persistent photoconductivity, which enhances the response time. Without a mismatch between the interface, the externally applied bias does not affect the dark current. This simple structure provides nice transmittance over 85% with a small external applied bias 1V that causes a 3-order on-off ratio. This work offers a highly transparent ZnO-based photoconductor with an excellent response speed. To the authors' knowledge, it is the first report about all ZnO-based UV photodetectors (Znic composition as metal is over 95%).
Wang et al. (Tue,) studied this question.