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 ~ 1017 cm−3. A large frequency downshift is observed when UV light irradiates the FBAR. With 365 nm UV light of intensity 1.7 mW/cm2, 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.
Highlights
A new type of ultraviolet (UV) light sensor based on film bulk acoustic wave resonator (FBAR) is proposed
D etection of ultraviolet (UV) radiation is very important in a number of areas such as UV radiation dosimetry, space-to-space communications, flame detection, UV astronomy, chemical/biological battle field reagent detectors, water purification, early missile threat warning, medicine, furnace control, and pollution monitoring[1,2] There are various types of UV sensors based on ZnO materials[3,4]
Film bulk acoustic wave resonator (FBAR) is a good choice for future UV sensing application owing to its high sensitivity and possibility of integration with CMOS technology
Summary
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 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. Film bulk acoustic wave resonator (FBAR) is a good choice for future UV sensing application owing to its high sensitivity and possibility of integration with CMOS technology. We believe that FBAR-based UV sensors with their excellent performance may increase their use. In this work, we studied two types of UV sensors using different FBAR device structures and will show that they possess excellent performance characteristics
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