Raman study of ZnxBe1−xSe solid solutions

Raman spectroscopy is used to identify the LO phonons of Zn x Be 1 . x Se/GaAs systems in a wide composition range. On the layer side a two-mode behavior is evidenced. The eigenfrequencies of the BeSe- and ZnSe-like LO modes correspond to the maxima of Im[-e(ω,x) -1 ]. Excellent agreement is obtained with a model based upon the modified random element isodisplacement (MREI) model. On the substrate side the LO mode couples with a plasmon (P) at the near-interface. The resulting LO-P mode is very sensitive to limit conditions at the junction. Below x ∼ 45% strong coupling is observed; above x ∼ 45% coupling is relaxed. The first behavior appears to be a marker for clean interfaces while the second one goes with the deposition of a thin highly disordered layer before the nominal Zn x Be 1-x Se is grown up to the surface.