Flattening of low temperature epitaxial Ge_(1-x)Sn_x/Ge/Si(l 00) alloys via mass transport during post-growth annealing

摘要

Epitaxial Ge_(1-x)Sn_x alloys were grown on Si(l 00) by MBE with a Ge buffer layer. The Ge buffer was grown by two step method using GeH_4 as gas source. The epitaxial layers were characterized by Rutherford Backscattering Spectrometry (RBS), Double Crystal X-ray Diffraction (DCXRD), and Atomic Force Microscopy (AFM) measurements. Then the Ge_(1-x)Sn_x alloys were annealed at 500℃ for times ranging from 0 to 10 min. During the annealing process, the surface morphology evolution, from three-dimensional round mounds to nearly two-dimensional ripples, and finally to flat, was observed. This result can be attributed to mass transport by surface diffusion.