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Published on: March 27, 2018
Tunable capacitors employing BZN/BST thin films for RF applications
Ruguan Li1, Shuwen Jiang, Libin Gao
1State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, China.
Tunable capacitors using bismuth zinc niobate/barium strontium titanate (BZN/BST) thin films offer high performance for radio frequency (RF) applications. These BZN/BST varactors show excellent tunability and quality factors, outperforming semiconductor diodes in phase shifters.
Area of Science:
- Materials Science
- Electrical Engineering
- Thin Film Technology
Background:
- Radio frequency (RF) applications require advanced tunable electronic components.
- Bismuth zinc niobate/barium strontium titanate (BZN/BST) thin films are promising materials for such applications.
Purpose of the Study:
- To investigate the performance of tunable parallel-plate capacitors utilizing BZN/BST thin films for RF applications.
- To evaluate the tunability, quality factor, and leakage current of BZN/BST-based varactors.
- To assess the suitability of these varactors in RF phase shifters.
Main Methods:
- Fabrication of parallel-plate capacitors with BZN/BST thin films.
- Intermediate frequency (IF) measurements to characterize device performance.
- Analysis of device quality factor dependence on electrode properties and frequency.
- Comparison of a phase shifter employing BZN/BST varactors with one using semiconductor diodes.
Main Results:
- BZN/BST varactors exhibited a large tunability of 39% at 40 V and a high device quality factor of 300 at 1 MHz.
- Devices maintained low leakage current density under high applied bias.
- Quality factor was found to be dependent on conductor loss of electrodes above 1 MHz.
- A phase shifter using BZN/BST varactors showed lower insertion loss compared to semiconductor diode-based designs at 445 MHz.
Conclusions:
- Tunable capacitors based on BZN/BST thin films demonstrate significant potential for RF applications.
- The high performance metrics of BZN/BST varactors make them suitable for advanced RF circuits.
- Further optimization of electrode materials could enhance device performance at higher frequencies.
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