Ultrasonic microspectroscopy characterization of AlN single crystals

Basic acoustic properties of AlN single crystal Y-cut and Z-cut plates, grown by the physical vapor transport method, were evaluated using ultrasonic microspectroscopy (UMS) technology. A method of determining the acoustical physical constants with two specimens was developed by measuring the velocities of longitudinal and shear waves and leaky surface acoustic waves (LSAWs). We obtained accurate bulk-wave velocities, LSAW velocities and their distributions in the specimen surfaces, and the density with great differences compared with the calculated ones using the reported constants. We also determined the corresponding constants. This UMS technology will contribute to the further development of AlN crystals.