Ultrasonic attenuation in INSB at very low temperatures

Abstract

Ultrasonic attenuation (x) as a function of bath temperature (0,1-100 K) and magnetic field (0-80 kG) has been measured in six n-type and four p-type InSb samples oriented along either the (111] or the [110] direction, and for longitudinal waves along the [111] or shear along the [110] direction in the range of 75 to 550 MHz. Samples excess carrier concentrations at 77 K ranged from 6,3x1013 to 7x1015 cm-3. Measurements of at very low temperatures confirm, in p-type samples, the existence of a temperature-induced relaxation peak and an attenuation decreasing with magnetic field. Inn-type we found a positive magnetic field-induced relaxation peak decreasing in amplitude and shifting towards lower fields as the temperature decreases. The results are well accounted for by the Hutson and White model. Free electrons and hopping are mainly responsible for the observed behaviour of the relaxation peaks as a function either of temperature or magnetic field. AC conductivity values derived from acoustic measurements agree not only with the existing models in the literature but also with our interpretation of the role played by the two forementioned processes in the Hutson and White model.