MODELLING OF ACOUSTODIFFUSIVE SURFACE WAVES IN PIEZOELECTRIC-SEMICONDUCTOR COMPOSITE STRUCTURES

We investigate the propagation of interfacial surface waves in a composite consisting of homogeneous isotropic semiconductor halfspace coated with a thin layer of homogeneous, transversely isotropic, piezoelectric material. The mathematical model of the problem consists of a coupled system of partial differential equations of motion, diffusion of electrons, and a Gauss equation along with the boundary conditions to be satisfied at the interface and free surface of the composite structure. The secular equation that governs the wave propagation at the interface has been obtained in compact form after solving the mathematical model analytically. The secular equations in the case of stress-free, isoconcentrated and stress-free, impermeable semiconductor halfspaces have also been deduced as special cases. The complex secular equation has been solved using the functional iteration method along with the irreducible Cardano's method via MATLAB programming for CdSe-Si, CdSe-Ge, PZT-Si and PZT-Ge composite structures. The computer-simulated results have been presented graphically in terms of phase velocity, attenuation coefficient, and specific loss factor of energy dissipation versus wave number and lifetime of charge carrier field in the considered structures. The work may be useful for the construction and design of surface acoustic wave devices.