Lattice Vibrational Properties of Crystalline Si–Ge Alloys

Abstract

The alloying and pressure dependences of Raman spectra due to optic modes of lattice vibration in crystalline Si–Ge alloys have been measured. The effect of alloying on the mode frequencies is interpreted by introducing the heteropolar term due to the effective charge into the interatomic interaction as well as taking account of the bond lengths expected from the EXAFS measurements. The asymmetry of the observed Raman spectral-line shape is discussed on the basis of the structural disorder with deviations of the bond lengths.