Lamb-wave mechanics in piezoelectric composite structures: Dispersion, attenuation, and asymmetry

In this paper, we investigate dispersion characteristics and mode shapes in semiconductor–piezoelectric laminates to elucidate wave–carrier interactions. Using the Stroh formalism together with the multidimensional moduli ratio convergence (MMRC) method, the complex dispersion equations of symmetric and asymmetric laminates are solved. A physics-informed calibration further relates attenuation peaks to the Maxwell time and Debye length through dimensionless groups, yielding testable design criteria. The results show that free carriers in the semiconductor layers significantly enhance acoustic attenuation while only weakly affecting the main propagation branches. More importantly, mode-shape analysis reveals how the electric potential in the piezoelectric film governs hole redistribution, clarifies the mode-shape exchange associated with branch veering, and explains why strong attenuation is restricted to specific mode families and narrow wavenumber intervals. In asymmetric laminates, geometric asymmetry additionally induces antisymmetry breaking in the electric-potential field.