ZnO Wheatstone bridge for UV light detection

Traditional UV detectors suffer from the disadvantage of large size or could not operate well without expensive UV filter. Therefore, the development of UV detectors with advantages of small size, operational without UV filter, voltage output and easy to integrate with signal processing IC chips, is of significant importance. In this paper, a ZnO bridge type UV detection unit is proposed and realized, by using four ZnO metal-semiconductor-metal (MSM) structured photoconductive devices as the four bridge arm of the Wheatstone bridge. First, the key manufacture processes are investigated by using discrete ZnO MSM photoconductive devices. The fabrication processes of the ZnO MSM bridge arm, the SiO2 passivation layer, and the ZnO light-shielding layer are optimized. By using these optimized fabrication processes, a ZnO bridge type UV detection unit is successfully realized and its UV response characteristics are tested. The results indicate that, this UV detection unit could respond to UV light power ranging from 1 μW to 6 mW, owning volume smaller than 1 mm3. The results in this paper demonstrates that the proposed small sized ZnO bridge type UV detection unit could operate very well without expensive UV filter and output a voltage signal directly, and is easy to integrate with signal processing IC chips as an integrated ZnO UV detection chip.