Effect of Carrier Trapping on the Weinreich Relation in Acoustic Amplification

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Abstract
The Weinreich relation between the acoustic absorption coefficient and the acoustoelectric field in semi‐conductors is found to be modified by carrier trapping. In the presence of dc fields, the acoustoelectric field and the absorption coefficient pass through zero at different values of drift field. The effects of the trapping are particularly important when the trapping time is of the same order as the acoustic‐wave period. The experimental evidence indicates that the above explanation for the effect of trapping is valid, with the dominant traps having a trapping time of about 10−9 sec. Some anomalies in the absorption were found which can be explained by the generation of a shear mode which does not interact with the carriers. Nonlinear interactions with this shear mode are found to occur at much lower power levels than those associated with second‐order effects in the theory of Hutson and White.