Isotope effects in elemental semiconductors: a Raman study of silicon

We present a comprehensive Raman study of self-energy effects in isotopically tailored silicon crystals at low temperature. Changes in the measured Raman spectra induced by isotope mass disorder are analyzed, including the weak excitations on the low-energy tail that arise approximately 30–60 cm−1 below the main Raman peak. In order to obtain a detailed picture of the renormalization, we simulate all lineshape properties within the framework of the coherent potential approximation. Comparison with earlier studies on diamond, germanium and α-tin illuminates the common aspects of isotope disorder-induced effects in elemental semiconductors.