Raman study of ZnxBe1-xSe solid solutions

Raman spectroscopy is used to identify the LO phonons of ZnxBe1-xSe/GaAs sy stems 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 corres pond to the maxims of Im[-epsilon(omega ,l)(-1)]. Excellent agreement is ob tained 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 c onditions at the junction. Below x similar to 45% strong coupling is observ ed; above x similar to 45% coupling is relaxed, The first behavior appears to be a marker for clean interfaces while the second one goes with the depo sition of a thin highly disordered layer before the nominal ZnxBe1-xSe is g rown up to the surface. (C) 2001 Elsevier Science B.V. All rights reserved.