Growth of relaxed GeSn film with high Sn content via Sn component-grade buffer layer structure

Abstract

Relaxed GeSn films with a high Sn content (>13%) were grown on Ge (100) substrates via magnetron sputtering epitaxy through a component-grade GeSn buffer layer structure. Raman spectroscopy, high-resolution x-ray diffraction, and cross-sectional transmission electron microscopy revealed that Ge0.861Sn0.139 alloys, with a degree of strain relaxation of up to 96.1%, can be achieved through a component-grade buffer layer structure. The threading dislocation density was estimated to be around 2×108 cm−2. The atomic surface flatness of the GeSn alloys was confirmed by atomic force microscopy, and the surface roughness was observed to be below 1 nm. Moreover, the thermal stability of GeSn samples was investigated. The results indicated that the component-grade structure is effective for realizing a high Sn composition and high relaxation of the GeSn alloy.