Basic mechanisms of acoustoresistive effect

Abstract

The analysis of the acoustoresistance experimental results carried by authors is presented in the paper. The change of electrical resistance under the action of the high frequency acoustic wave (AW) is called an acoustoresistive effect (ARE). In difference of the acoustoelectric effect the phenomena of ARE is not galvanic. The ARE is observed in semiconductors: Ge, Si, CdS, CdSe etc. and in layered structures: piezoelectric and semiconductor. The maiden experimental work on acoustoresistivity was done by authors in 1967 year [9] and it was the beginning of the acoustoresistivity investigations. The analysis of experimental data is based on the crystal and its energetic levels modulation; the reason of this phenomena is piezoeffect and deformation potential. In the paper the main attention is given to piezosemiconductors and to the layered piezoelectric-semiconductor structures. Some basic mechanisms of acoustoresistive effect are presented. The acoustoresistive effect in the high photosensitive semiconductors is accounted. In these materials the ARE is determined(caused) by modulation of the trapping and recombination levels in the band gap. The model with one recombination level was discussed in works of Y. V. Gulyaev [4, 5] et theoretically. and negative ARE is provided. The ARE is caused by the charge carriers ejection induced by AW. The strong positive ARE, as provided in model with two recombination levels, is observed experimentally. In this case the ARE is caused by the acoustic damping of photoconductivity. The strongest ARE is observed in layered structures with thin films where the resistance of film under the action of AW changes twice. In the layered structures the reason of the ARE is the change of (1) intercrystalline barriers and (2) surface electrokinetic process conditions by the propagating AW. Both the positive and the negative ARE is observed. The new type sensors on the base of acoustoresistive effect are created. Fig. 8. Ref. 18.