ACOUSTICAL DISSIPATION IN SOME TETRAHEDRALLY-BONDED SEMICONDUCTING COMPOUNDS

Phonon-phonon coupling and thermoelastic relaxation are the principal thermal causes of ultrasonic attenuation in solids at room temperature . Second order elastic moduli and third order elastic moduli have been used to study the ultrasonic attenuation suffered by compressional an d shear acoustic waves for some tetrahedrally bonded semiconducting ma terials, viz. GaP, InP and InAs along (100), (110) and (111) crystallo graphic directions. Attenuation in case of InP is found to be quite la rge as compared to GaP and InAs. The reason behind this discrepancy is due to doping of Cr in InP sample and it is also seen that ultrasonic , attenuation due to phonon-phonon interaction dominates over that due to thermoelastic relaxation.