Abstract
If an applied electric field in a piezoelectric semiconductor causes the drift velocity of the carriers to exceed the sound velocity, then acoustic waves travelling in the direction of the drifting carriers will be amplified. This phenomenon is called the acoustoelectric effect [1, 2]. This effect also applies to spontaneously generated waves with thermal amplitudes. These amplified acoustic waves interact with the free carriers. This gives rise to current saturation and large current and acoustic noise [3, 4]. The acoustoelectric effect was first described by WHITE [2]. White’s theory, however, is essentially a linear, small-signal theory and does not describe the occurrence of current saturation and the concommittant large current and acoustic noise. A complete description involves non linear effects, including the piezoelectric relations and the wave equation. Up till now, however, noone has been successful in developing such a theory. Instead models were used. MOORE [5] constructed a two-state, two parameter phenomenological model by combining the concept of carrier bunching [6, 7] in potential troughs associated with the locally generated incoherent acoustic waves with a form of generation-recombination noise process. The expression for the noise data thus obtained gives a reasonable explanation for Moore’s experimental data on n-type CdS.
Published Version
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