Relaxation Attenuation of Ultrasonic Waves in InAs

Abstract

The attenuation of longitudinal and transverse ultrasonic waves with frequencies between 90 and 510 MHz and propagating in the [110] direction in InAs has been measured at room temperature. Measurements were also made at lower temperatures employing 210-MHz longitudinal waves. The attenuation at room temperature is observed to increase less strongly than ${f}^{2}$, where $f$ is the frequency. However, when the residual attenuation observed at 4.2 K is subtracted from the room-temperature data, the difference approaches the ${f}^{2}$ dependence expected for the Akhieser phonon viscosity mechanism. It is found that the temperature dependence of the attenuation can also be accounted for within the framework of the Akhieser mechanism and is due mainly to the quantity $\ensuremath{\Sigma}{i}^{}{\ensuremath{\gamma}}_{i}^{2}{C}_{{V}_{i}}$, where the ${\ensuremath{\gamma}}_{i}$'s and ${C}_{{V}_{i}}$'s are the Gr\uneisen $\ensuremath{\gamma}$'s and heat capacities of a small number of Debye continua and Einstein modes by which the actual phonon spectrum can be approximated.