We report polycrystalline diamond epitaxial growth on β -Ga 2 O 3 for device-level thermal management. We focused on establishing diamond growth conditions on β -Ga 2 O 3 accompanying the study of various nucleation strategies. A growth window was identified, yielding uniform-coalesced films while maintaining interface smoothness. In this first demonstration of diamond growth on β -Ga 2 O 3 , a diamond thermal conductivity of 110 ± 33 W m −1 K −1 and a diamond/ β -Ga 2 O 3 thermal boundary resistance of 30.2 ± 1.8 m 2 K G −1 W −1 were measured. The film stress was managed by growth optimization techniques preventing delamination of the diamond film. This work marks the first significant step towards device-level thermal management of β -Ga 2 O 3 electronic devices.

Radio frequency (RF) microelectromechanical systems (MEMS) based on Al1-xScxN are replacing AlN-based devices because of their higher achievable bandwidths, suitable for the fifth-generation (5G) mobile network. However, overheating of Al1-xScxN film bulk acoustic resonators (FBARs) used in RF MEMS filters limits power handling and thus the phone's ability to operate in an increasingly congested RF environment while maintaining its maximum data transmission rate. In this work, the ramifications of tailoring of the piezoelectric response and microstructure of Al1-xScxN films on the thermal transport have been studied. The thermal conductivity of Al1-xScxN films (3-8 W m-1 K-1) grown by reactive sputter deposition was found to be orders of magnitude lower than that for c-axis-textured AlN films due to alloying effects. The film thickness dependence of the thermal conductivity suggests that higher frequency FBAR structures may suffer from limited power handling due to exacerbated overheating concerns. The reduction of the abnormally oriented grain (AOG) density was found to have a modest effect on the measured thermal conductivity. However, the use of low AOG density films resulted in lower insertion loss and thus less power dissipated within the resonator, which will lead to an overall enhancement of the device thermal performance.