Raman scattering study of amorphous GeSn films and their crystallization on Si substrates

Abstract The dependence of Raman scattering spectra on Sn composition in the amorphous Ge 1-x Sn x films deposited on Si(001) substrates by magnetron sputtering is investigated. Two broad phonon scattering peaks are clearly observed, which are attributed to the disordered Sn Sn and Ge Ge bonds, shifting to lower wavenumbers with the increase of Sn content. The ratio of integrated intensity of Sn Sn to Ge Ge modes increases linearly with Sn content in the range of 0.06 to 0.2. With rapid thermal annealing, although the critical crystallization temperature becomes lower for higher Sn content amorphous GeSn, severe Sn segregation occurs for all of the samples. Relative lower crystallization temperature is proved to be beneficial for tailoring high Sn content crystalline GeSn films. Polycrystalline GeSn alloys with maximum substitutional Sn content of 0.07 are achieved with an annealing temperature of 400 °C.