Epitaxial Single-Crystal ScAlN on 4H-SiC for High-Velocity, Low-Loss SAW Devices

This report presents some of the first experimental characterization of surface acoustic wave (SAW) devices using single-crystal ScAlN epitaxially grown on SiC. Due to the excellent wave guiding provided by the ScAlN/SiC heterostructure, SAW phase velocities greater than 12,000 m/s are measured, higher than comparable ScAlN SAW devices on other substrates. The phase velocity dispersion for measured devices compares well with simulated values. We observe up to $k^{2}=0.52{\%}$ even for very small thickness to wavelength ratios ($t/\lambda < 0.2$). We show that epitaxial ScAlN/SiC can achieve extremely low SAW propagation loss ($\alpha < 10^{-2}\ dB/\lambda$), comparable to state-of-the-art piezoelectric/diamond SAW devices, and are linear at CW RF power levels up to ≈30 dBm (1W), with 1 dB gain compression at 34 dBm and an IIP3 of 45 dBm.