Impact of Sn incorporation on sputter epitaxy of GeSn

Epitaxial growth of high-quality low tin content germanium (GeSn) alloy is demonstrated by sputter deposition. Adding several percent of Sn during simultaneous sputter deposition significantly improved the crystallographic structure of the GeSn alloy, leading to intense photoluminescence even at room temperature. Dislocation-free single-crystal GeSn films were formed on a Ge(100) substrate under tuned growth conditions, that is, an Sn/Ge flux ratio of 6.2% and deposition temperature of 500 °C, in which compositional gradation of the Sn content in the film thickness direction spontaneously formed. The growth mechanisms are discussed based on growth kinetics and Sn diffusion on the growing surface.