title: Gigahertz acoustic wave velocity measurement in GaN single crystals considering acousto-electric effect.
abstract: The resistivity-frequency characteristics of longitudinal wave velocities propagating parallel to the c-axis in a GaN single crystal were theoretically estimated by considering the piezoelectric acousto-electric effect. The temperature and frequency dependences of longitudinal and shear wave velocities in conductive and semiconductive GaN single-crystal samples were experimentally investigated by Brillouin scattering. The temperature dependence of longitudinal and shear wave velocities had a linear tendency in the conductive sample, whereas in the semiconductive sample, those had a similar tendency to the predicted velocity changes resulting from the piezoelectric stiffening effect. However, the temperature dependence of shear wave velocity, which does not possess piezoelectric coupling, had a tendency similar to that of the longitudinal wave in the semiconductive sample, unexpectedly. The frequency dependence of longitudinal wave velocities in the semiconductive sample had a tendency similar to the predicted velocity changes resulting from the piezoelectric stiffening effect.
authors: Hayato
authors: H
authors: Ichihashi
authors: Takahiko
authors: T
authors: Yanagitani
authors: Shinji
authors: S
authors: Takayanagi
authors: Masahiko
authors: M
authors: Kawabe
authors: Mami
authors: M
authors: Matsukawa