Modeling of gallium arsenide surface acoustic wave devices

A Surface-Acoustic Wave (SAW) device has been modeled employing a secondorder Lagrangian finite-element method. The model is able to describe SAW response variations with arbitrary orientation of the unit crystal cell as compared to the macroscopic device geometry and hence allows for fast SAW design optimization. The model is used to determine the resonance frequency of different SAW device structures. The finite-element results are compared with independent analytical results obtained for two configurations of the applied electrode voltages. In order to obtain significant excitation of SAWs, it is preferable to have the electrode fingers oriented along the [110] crystal axis direction, which is the direction along the x=y line with z constant. Indeed, characteristics of normal displacement amplitudes as a function of rotation angle between the crystal axes and the electrode fingers at a fixed frequency albeit independent of the frequency verify that strong SAW excitations take place for rotation angles near 45 degrees corresponding to the [110] direction. Computations of various eigenmodes of both Rayleigh and Lamb type are discussed.