Leaky surface acoustic waves in single-crystal AlN substrate

We report on the velocity V and the electromechanical coupling coefficient K-2 of the first and the second leaky surface acoustic waves in various propagation directions in the a-plane AIN single-crystal. For cpropagation direction, the second leaky wave exhibited the velocity of 11016 m/s and K-2 of 0.45%. For this direction, the temperature coefficient of frequency was found to be -30 ppm/degrees C. A near match of the velocities of the plane and leaky waves in the a-plane AIN allowed us to establish analytical relationships between the piezoelectric and elastic constants. A full set of elastic and piezoelectric constants of AIN has been evaluated by fitting the measured and calculated dependencies of velocities and electromechanical coupling coefficients on the propagation direction for both Rayleigh and leaky waves.