Structural and optical characterization of Si xGe 1-x-ySn y alloys grown by molecular beam epitaxy

Abstract

Si xGe 1-x-ySn y alloys were grown by molecular beam epitaxy at low temperature, followed by ex-situ annealing. The crystal quality of Si xGe 1-x-ySn y layers was characterized by atomic force microscopy and transmission electron microscopy. The compositions and lattice constants of the alloys were studied by x-ray photoelectron spectroscopy and x-ray diffraction. The results show that Vegard's law is a good approximation for Si xGe 1-x-ySn y alloys. Photoreflectance spectroscopy at room temperature was used to determine the direct bandgap energy of Si xGe 1-x-ySn y layers. Analyzing the relationship between composition and direct bandgap energy reveals a negative energy bowing parameter for SiSn. © 2012 American Institute of Physics.