Re-examination of the SiGe Raman spectra: Percolation/one-dimensional-cluster scheme and ab initio calculations

We report on the detailed assignment of various features observed in the Raman spectra of SiGe alloys along the linear chain approximation (LCA), as achieved based on remarkable intensity interplays with composition between such neighboring features known from the literature but which so far have not been fully exploited. Such an assignment is independently supported by ab initio calculation of the frequencies of bond-stretching modes taking place in different local environments, which we define at one dimension (1D) for consistency with the LCA. The SiGe vs GaAsP comparison is supported by ab initio calculation of the local lattice relaxation/dynamics related to prototype impurity motifs that are directly transposable to the two crystal structures.