AlN Material Constants Evaluation and SAW Properties on AlN/Al<inf>2</inf>O<inf>3</inf>and AlN/Si

Abstract

We have determined the material constants of AlN,i.e., elastic stiffness, piezoelectricity and permittivity, by computer calculation from the experimental results on SAW phase velocities and electromechanical coupling coefficients. A1N films used were single-crystal films on the basal plane of sapphire grown by metalorganic chemical vapor deposition. Until now, very few of these material constants are known. We report, for the first time, all the matrix elements of the material constants. The calculated variations of SAW phase velocities and coupling constants with A1N film thickness on basal and R planes of sapphire were in good agreements with the reported experimental results. Next, using the evaluated material constants, it was shown that the highfrequency (UHF) and low-dispersion SAW characteristics (less than 0.1% velocity change for ~20% bandwidth) with a large coupling (4%) can be expected for AlN/Si and AlN/SOS, when the c-axis of A1N was aligned along the surface of (001) Si.