Flattening of low temperature epitaxial Ge1−xSnx/Ge/Si(1 0 0) alloys via mass transport during post-growth annealing

Epitaxial Ge1−xSnx alloys were grown on Si(1 0 0) by MBE with a Ge buffer layer. The Ge buffer was grown by two step method using GeH4 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 Ge1−xSnx alloys were annealed at 500 °C 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.