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

• Published in: Scientific reports Vol. 5; no. 1; p. 9123
• Main Authors: Bian, Xiaolei, Jin, Hao, Wang, Xiaozhi, Dong, Shurong, Chen, Guohao, Luo, J. K., Deen, M. Jamal, Qi, Bensheng
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 16.03.2015; Nature Publishing Group
• Subjects: 142/126; 147/135; 639/166/987; 639/301/1005/1007; 639/301/1005/1009; 639/766/1130/2798; Capacitance; Circuits; Humanities and Social Sciences; Light; multidisciplinary; Science; Sensors
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/srep09123

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.