The Nonlinear Acoustoelectric Effect in a Superlattice

The acoustoelectric effect in a superlattice (SL) is investigated for an acoustic wave whose wavelength $\lambda =2\pi/ q$ is smaller than the mean free path $l$ of the electrons and hypersound in the region $ql\gg1$. (where $ q$ is the acoustic wave number) . A nonlinear dependence of the acoustoelectric current $j^{ac}$ on the constant electric field $E$ is obtained by using the classical Boltzmann kenetic equation. The analytical expression for the acoustoelectric current $j^{ac}$ is calculated for constant of momentum relaxation time. Numerical calculations is done, and the result is discussed for a typical GaAs/AlGaAs SL. It is noted that when the electric field is negative the current $j^{ac}$ decreases, reaches a minimum and rises. On the other hand, when the electric field is positive the current increases, reaches a maximum and then falls off. A similar observation has been noted for an acoustoelectric interaction in a multilayered structure resulting from the analysis of $Si/SiO_{2}$ structure. The dominant mechanism for such a behavior is attributed to the periodicity of the energy spectrum of electron along the SL axis.