Determination of Mass Density, Dielectric, Elastic, and Piezoelectric Constants of Bulk GaN Crystal

Mass density, dielectric, elastic, and piezoelectric constants of bulk GaN crystal were determined. Mass density was obtained from the measured ratio of mass to volume of a cuboid. The dielectric constants were determined from the measured capacitances of an interdigital transducer (IDT) deposited on a Z-cut plate and from a parallel plate capacitor fabricated from this plate. The elastic and piezoelectric constants were determined by comparing the measured and calculated SAW velocities and electromechanical coupling coefficients on the Z- and X-cut plates. The following new constants were obtained: mass density rho = 5986 kg/m(3); relative dielectric constants (at constant strain S) epsilon(S)(11)/epsilon(0) = 8.6 and epsilon(S)(33)/epsilon(0) = 10.5, where epsilon(0) is a dielectric constant of free space; elastic constants (at constant electric field E) c(11)(E) = 349.7, c(12)(E) = 128.1, c(13)(E) = 129.4, c(33)(E) = 430.3, and c(44)(E) = 96.5 GPa; and piezoelectric constants e(33) = 0.84, e(31) = -0.47, and e(15) = -0.41 C/m(2).