High-temperature 434 MHz surface acoustic wave devices based on GaPO₄

Abstract

Research into surface acoustic wave (SAW) devices began in the early 1970s and led to the development of high performance, small size and high reproducability devices. Much research has now been done on the application of such devices to consumer electronics, process monitoring and communication systems. The use of novel materials such as gallium phosphate (GaPO4), extends the operating temperature of the elements. SAW devices based on this material operating at 434 MHz up to 800C, can be used for passive wireless sensor applications. Interdigital transducer (IDT) devices with Platinum/ Zirconium metallization and 1.4 micron finger-gap ratio of 1:1 have been fabricated using direct-write e-beam lithography and a lift-off process. The performance and long term stability of these devices has been studied, and the results are reported in this paper