Measurements of the acoustic gain parameters in n-InSb

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Abstract
The drift‐velocity dependence of the acoustic gain in n‐InSb at 77°K is derived from measurements of the rate of growth of the acoustoelectric field in the sample under constant‐current pulses of different amplitudes. The amplified acoustic flux monitored by the acoustoelectric field originates from the thermal‐equilibrium phonon distribution in the crystal. Results obtained for samples of different carrier concentrations are compared with the predictions of microscopic theories applicable to InSb (ql> 1). For low drift velocities the agreement between theory and experiment is very good. For drift velocities approaching the thermal velocity, on the other hand, the experimental data deviate markedly from the theoretical predictions. In this range appreciable carrier heating takes place, an effect that has not been adequately taken into account in the existing theories. The data also provide estimates for the nonelectronic (lattice) attenuation factor and for the initial thermal flux density. The values obtained for the latter are within an order of magnitude of those calculated on the basis of the thermal‐equilibrium Debye spectrum.