Cryogenic enhancement of phononic four-wave mixing in AlScN/SiC

TL;DR

This study demonstrates cryogenic temperature enhances phononic four-wave mixing in AlScN/SiC heterostructures, with mode-dependent nonlinearities, advancing the development of nonlinear phononic systems for signal processing.

Contribution

It provides the first comparison of temperature-dependent nonlinear behavior in AlScN/SiC heterostructures, highlighting mode-specific enhancements at cryogenic temperatures.

Findings

Nonlinear coefficient increases at 4 K for both modes.

Rayleigh mode exhibits two orders of magnitude larger nonlinearity than Sezawa mode.

Temperature, mode confinement, and strain localization significantly influence phononic nonlinearity.

Abstract

Surface acoustic wave platforms based on piezoelectric thin-film heterostructures provide sub-wavelength acoustic confinement, making them attractive for compact nonlinear phononic systems with applications including frequency conversion, parametric interactions, and nonlinear signal processing. Here, we investigate guided surface acoustic wave phononic four-wave mixing at gigahertz frequencies in an aluminum scandium nitride/4H-silicon carbide heterostructure operated at both room temperature (295 K) and cryogenic temperature (4 K). The 500 nm thick aluminum scandium nitride film supports guided Rayleigh and Sezawa modes with distinct displacement and strain energy density distributions, allowing a direct comparison of mode-dependent nonlinear behavior within the same device. Continuous-wave four-wave mixing measurements reveal an enhancement in the extracted modal nonlinear coefficient at 4 K relative to 295 K for both modes. In addition, the Rayleigh mode exhibits a modal nonlinearity approximately two orders of magnitude larger than that of the Sezawa mode across both temperature regimes. These results demonstrate that phononic four-wave mixing is strongly influenced by temperature, mode confinement, and strain localization while establishing aluminum scandium nitride on silicon carbide heterostructures as a promising platform for engineering enhanced nonlinear phononic interactions for future classical and quantum acoustic on-chip signal processing systems.