ACOUSTOELECTRIC EFFECT IN A SEMICONDUCTOR SUPERLATTICE

The acoustoelectric effect in a semiconductor superlattice has been studied for an acoustic wave whose wavelength lambda = 2pi/q is smaller than the mean free path l of the electrons (where ql much greater than 1). Unlike the homogeneous bulk material where the Weinreich relation is independent of the wavenumber q in the superlattice we observe a dependence on q, i.e. spatial dispersion. In the presence of an applied constant field E a threshold value was obtained where the acoustoelectric current changes direction.