Gallium nitride phononic integrated circuits for future RF front-ends

TL;DR

This paper demonstrates the use of gallium nitride phononic circuits to guide high-frequency sound in micrometer-scale waveguides, enabling monolithic integration of RF components for future mobile communication systems.

Contribution

It introduces a novel approach to guide high-frequency sound in GaN waveguides, facilitating monolithic RF front-end integration in GaN-on-SiC platforms.

Findings

High-frequency sound (>3 GHz) can be efficiently guided in GaN waveguides.

GaN phononic circuits enable significant size reduction of RF passives.

Potential for monolithic integration of RF front-ends in GaN-on-SiC.

Abstract

Achieving monolithic integration of passive acoustic wave devices, in particular RF filters, with active devices such as RF amplifiers and switches, is the optimal solution to meet the challenging communication requirements of mobile devices, especially as we move towards the 6G era. This requires a significant ($\approx$100x) reduction in the size of the RF passives, from mm$^2$ footprints in current devices to tens of ${\mu}m^2$ in future systems. Applying ideas from integrated photonics, we demonstrate that high frequency (>3 GHz) sound can be efficiently guided in ${\mu}$m-scale gallium nitride(GaN) waveguides by exploiting the strong velocity contrast available in the GaN on silicon carbide (SiC) platform. Given the established use of GaN devices in RF amplifiers, our work opens up the possibility of building monolithically integrated RF front-ends in GaN-on-SiC.