The Phonon Percolation Scheme for Alloys: Extension to the Entire Lattice Dynamics and Pressure Dependence

Abstract

We explore two basic issues behind the 1-bond -> 2-mode percolation scheme that has recently lead to a unification of the classification of the Raman and infrared spectra of usual zincblende semiconductor alloys. In doing so we focus on the model ZnBeSe alloy, for which the percolation scheme was originally developed. First, we show by using inelastic neutron scattering that the well-resolved 1-bond -> 2-mode percolation doublet of the short Be-Se bond detected close to the zone center by Raman and infrared spectra remains observable throughout the whole Brillouin zone up to the zone edge. This testifies for an origin at the bond scale. Second, high-pressure is used to disable a Fano interference which screens the Zn-Se Raman signal, revealing a distinct Zn-Se percolation doublet. This provides experimental evidence that the 1-bond -> 2-mode percolation scheme is generic, and may, in principle, apply to all bonds in an alloy.