Phonon dispersion of bulk Ge-rich SiGe: Inelastic X-ray scattering studies

Group IV semiconductors, such as SiGe with a higher Ge fraction, are attracting attention as next-generation materials for high-mobility channel or thermal conductivity devices. Thus, we investigated the phonon dispersions of a Si1-xGex (x = 0.72) alloy crystal by the inelastic X-ray scattering (IXS) method. In this method, measurement with an X-ray beam with a small spot size of 75 mu m and resolution of millielectronvolts is possible due to the synchrotron technique. The longitudinal and transverse phonon spectra of optical and acoustic modes were measured from the Gamma to the X point in the phonon energy band (0-70 meV) with millielectronvolt energy resolution. SiGe showed dispersion characteristics similar to those of Si and Ge crystals. It was confirmed that the IXS method is useful for obtaining properties of phonon dispersion.