Investigation of thin film surface acoustic wave devices of AlN/GaN/Sapphire
| Autor: | Wei-Cheng Chien, 簡維政 |
|---|---|
| Rok vydání: | 2005 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 93 In recent years, surface acoustic wave devices have become an attractive research field because the devices can be applied in communication field, and it suits to be sensors for it’s high sensitivity. Using piezoelectric thin films for layered structure SAW devices is popular. AlN thin films have been deposited on GaN/Sapphire for SAW devices by using Helicon sputtering system. GaN is a semiconductor with piezoelectric properties. However, its relatively large electrical conductivity and unavoidable residual dopants during the thin film growth have been the obstacles for the application of SAW devices made on GaN. AlN is the promising material for SAW devices due to its excellent piezoelectricity, high surface acoustic wave velocity, substantial electromechanical coupling coefficient, good thermal stability. Due to the small lattice mismatch between AlN and GaN, epitaxial AlN films can be deposited on GaN. Superior SAW characteristics have been obtained by deposition AlN on GaN. The thin film layered structure for SAW devices, with the combination of AlN and GaN may, in future, bring about the development of high frequency components which integrate and utilize their semiconducting, optoelectronic properties. The effects of thickness of AlN thin films have been discussed in terms of the insertion loss、sidelobe rejection、phase velocity and electromechanical coupling coefficient. The TCF of GaN/sapphire and AlN/GaN/Sapphire have been measured as well. The results showed that the loss and sidelobe rejection of the SAW devices can be improved by increasing the thickness of AlN films. The TCF of AlN on GaN was found to be positive, and by increasing the thickness of AlN, the TCF of the combination of AlN and GaN/Sapphire be compensated, which may contribute to the applications of this layered structure SAW devices. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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