SAW chemical sensors based on AlGaN/GaN piezoelectric material system: acoustic design and packaging considerations

In this paper, we present the modeling of the mechanical part of a MEMS (microelectromechanical systems)-based sensor for identifying environmental contaminants and chemical or biological agents in large applications scale. The mechanical part involves the structure for the generation and reception of the surface acoustic wave likewise the packaging and housing structure of the sensor. Sensor detection mechanism is based on the changes of the surface acoustic wave (SAW) propagation along the substrate. By using various coatings on the surface of the SAW device, various cells, chemicals, gases and bio materials can be detected due to changes of the velocity or phase of a propagating acoustic wave induced by the outer environment. The AlGaN/GaN material system preferentially grown on both silicon and sapphire (Al/sub 2/O/sub 3/) substrates by metal organic vapor phase epitaxy (MOCVD) or by molecular beam expitaxy (MBE) is a promising platform for fabrication of a new generation of wireless SAW sensor devices. This implicate the development of high electron mobility transistor (HEMT) structure integrated in a single chip with the SAW sensor and thus creating a unique acoustic velocity tuning device with low acoustic loss and high frequency.