Formation and properties of GeSn:C films on silicon substrates

The paper reports the formation of GeSn:C films on silicon substrates by thermal spraying of Ge/Sn superlattices followed by implantation of C+ ions into them and annealing at 350 degrees C. It is shown that compared to Ge films, the crystallization temperature of which is -500 degrees C, the crystallization temperature of the GeSn and GeSn:C films is significantly reduced, down to 300 and 350 degrees C, respectively. We explain this effect by the diffusion of tin atoms in the Ge lattice, which decreases the activation energy of the Ge crystallization process. Implantation of C+ ions into a Ge/Sn superlattice reduces the effect of Sn atoms on the crystallization process and, accordingly, increases the crystallization temperature. We have confirmed experimentally that implantation of C+ ions in Ge/Sn structures contributes to the reduction of local stresses in the Ge lattice induced by the incorporation of Sn atoms and thus possibly increases the concentration of incorporated Sn atoms in the Ge lattice. It has been established as well that laser annealing of Ge/Sn structures implanted with C+ ions is more effective for embedding Sn atoms in the Ge lattice as compared to thermal annealing.