Second harmonic of the acoustoelectric current in piezosemiconductors

Abstract

The second harmonic of the acoustoelectric current generation J(2ω) as a consequence of electronic concentration nonlinearity during the propagation of elastic waves at frequency ω in piezosemiconductors is investigated both, theoretically and experimentally. Bulk waves and waves in the acoustic waveguides are considered. It is shown that the current J is directly proportional to the power and electronic attenuation of the ultrasound and to the drift mobility of carriers. In the acoustic waveguides the current J is subjected to a strong dispersion and tends to zero while ω tends to the cut‐off frequency of the mode. Under small electronic attenuation J ∼ sin kL/kL (where k is a wave number, L the length of electron‐phonon interaction) for all types of waves discussed, i.e. the so‐called “size effect” takes place. From the measuring period Δω of the function J(kL) the wave phase velocity may be determined. Results of the experiments carried out on shear bulk waves and waves in thin plates of CdS show good agreement with theoretical calculations.

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