Theory of Raman Scattering from Plasmons Polaritons in GaAs/AlxGa1-xAs Superlattices
When layers of the alloy in epitaxially-grown GaAs/AlxGa1-x As super-lattices are modulation-doped with Si during the growth process, the donor electrons lead to the assembly of a periodic array of electron layers separated by dielectric layers. Such a system of electrons is capable of exhibiting plasma oscillations, the existence of which has been substantially confirmed by Raman measurements. The theory pertaining to this experimental situation is examined here using linear-response methods which we apply to two theoretical models of the superlattice. The first model assumes a strictly two-dimensional picture of the electron layers and this turns out to be a good approximation for a fairly comprehensive analysis of the various aspects exhibited by the first results due to Olego et al. The second model incorporates the effects of a finite thickness for the electron layers. This is shown to lead to better agreement with experiment. The theory yields predictions on the energy, integrated intensity and shape of the observed Raman peak. Furthermore, it leads to the prediction of a second plasmon branch which we suggest may have already been exhibited by experimental results due to Olego et al. and Sooryakumar et al.
KeywordsDispersion Relation Green Function GaAs Layer Linear Response Theory Plasmon Peak
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