Reduction of surface acoustic wave grating impedance and velocity perturbations via buried bimetallic electrode geometries

Abstract

The impedance and velocity perturbations presented to the leaky wave by the nondestructive sense (NDS) electrodes in GaAs acoustic charge transport (ACT) devices are of particular concern in the design of high quality ACT devices. An example is shown where large perturbations and improperly designed NDS arrays resulted in substantial leaky wave propagation loss. The full form of the Datta and Hunsinger velocity and impedance perturbation equations is presented for the case of buried bimetallic grating arrays and it is shown that, with the proper choice of groove depths and metal thicknesses, it is theoretically possible to simultaneously reduce the impedance and velocity perturbations to negligible values. It is by such a procedure that a ‘‘perturbationless’’ array can be made. Laser probe measurements of the reflection coefficient and velocity perturbation for three buried chrome-gold grating devices demonstrate the feasibility of achieving this theoretical ideal.