Unveiling Carrier-Mediated Acoustic Leakage as a Hidden Loss Pathway in Piezoelectric-Semiconductor Heterostructures.

Heterogeneous integration of dissimilar functional materials enables advanced micro/nano devices with unprecedented functionalities, yet the resulting interfacial multiphysics interactions can introduce hidden energy leakage pathways beyond conventional bulk systems. Here, we reveal a previously overlooked carrier-mediated acoustic leakage mechanism in piezoelectric-semiconductor heterostructures. By developing an electromechanical-carrier coupling model, we demonstrate that interfacial carrier accumulation reconstructs electrical boundary conditions, causing piezoelectric fields to penetrate into non-resonant regions. The resulting electric field distortion activates parasitic mechanical vibrations, which radiate bulk acoustic waves into the silicon substrate and degrade the quality (Q) factor. Ultrafast femtosecond laser pump-probe spectroscopy is further employed to characterize carrier dynamics, establishing a quantitative link between carrier modulation and acoustic performance. Guided by this mechanism, multiphysics decoupling strategies based on material engineering and electric field engineering are developed to suppress carrier-mediated acoustic leakage. By reconstructing electrical boundaries through defect-state modulation and asymmetric electrode design, the Q factor of piezoelectric-semiconductor devices is substantially enhanced while maintaining compatibility with standard fabrication processes. This work reveals an unconventional role of semiconductor carriers as mediators of acoustic energy redistribution and provides a mechanism-guided strategy for designing high-performance heterogeneously integrated micro/nano devices.