UV sensing using film bulk acoustic resonators based on Au/n-ZnO/piezoelectric-ZnO/Al structure

Xiaolei Bian; Hao Jin; Xiaozhi Wang; Shurong Dong; Guohao Chen; J K Luo; M Jamal Deen; Bensheng Qi

doi:10.1038/srep09123

UV sensing using film bulk acoustic resonators based on Au/n-ZnO/piezoelectric-ZnO/Al structure

Sci Rep. 2015 Mar 16:5:9123. doi: 10.1038/srep09123.

Authors

Xiaolei Bian¹, Hao Jin¹, Xiaozhi Wang¹, Shurong Dong¹, Guohao Chen¹, J K Luo², M Jamal Deen³, Bensheng Qi⁴

Affiliations

¹ Dept. of Info. Sci. &Electr. Eng., Zhejiang University and Cyrus Tang Center for Sensor Materials and Applications, 38 Zheda Road, Hangzhou 310027, China.
² 1] Dept. of Info. Sci. &Electr. Eng., Zhejiang University and Cyrus Tang Center for Sensor Materials and Applications, 38 Zheda Road, Hangzhou 310027, China [2] Institute of Renewable Energy &Environ. Technol., Univ of Bolton, Bolton, BL3 5AB, UK.
³ 1] Dept. of Info. Sci. &Electr. Eng., Zhejiang University and Cyrus Tang Center for Sensor Materials and Applications, 38 Zheda Road, Hangzhou 310027, China [2] Electrical and Computer Engineering, McMaster University, Hamilton, ON L8S 4K1, Canada and ECE Department, Hong Kong University of Science and Technology, Kowloon, Hong Kong.
⁴ College of Internet of Things Engineering, Hohai University, Changzhou, 213022, China.

Abstract

A new type of ultraviolet (UV) light sensor based on film bulk acoustic wave resonator (FBAR) is proposed. The new sensor uses gold and a thin n-type ZnO layer deposited on the top of piezoelectric layer of FBAR to form a Schottky barrier. The Schottky barrier's capacitance can be changed with UV light, resulting in an enhanced shift in the entire FBAR's resonant frequency. The fabricated UV sensor has a 50 nm thick n-ZnO semiconductor layer with a carrier concentration of ~ 10(17) cm(-3). A large frequency downshift is observed when UV light irradiates the FBAR. With 365 nm UV light of intensity 1.7 mW/cm(2), the FBAR with n-ZnO/Au Schottky diode has 250 kHz frequency downshift, much larger than the 60 kHz frequency downshift in a conventional FBAR without the n-ZnO layer. The shift in the new FBAR's resonant frequency is due to the junction formed between Au and n-ZnO semiconductor and its properties changes with UV light. The experimental results are in agreement with the theoretical analysis using an equivalent circuit model of the new FBAR structure.