Temperature and Frequency Dependence of Acoustic Attenuation in Pure Semiconductors

Real solids show a deviation from perfectly elastic behavior and exhibit anharmonicity due to existence of zero-point energy, owing to which, a stress wave in the form of high frequency acoustic wave, travelling through it, gets attenuated. In the present work, some acoustic properties of pure semiconductors germanium and silicon, are investigated within temperature range 73-293 K, by making use of second and third order elastic constants. Assuming a temperature dependent non-linearity parameter D_L, D_S, the acoustic wave attenuation 'A' is calculated for longitudinal waves of frequency 286 MHz and 495 MHz and for shear waves of 495 MHz, propagating in pure germanium and silicon. The Akhieser losses leading to attenuation are attributed mainly to phonon-phonon interactions within the solid. Attenuation of high frequency waves is found to be strongly temperature and frequency dependent. Theoretically calculated values of attenuation 'A' show good agreement with experimental values obtained earlier.