Growth of Ge1−xSnx/Ge strained-layer superlattices on Si(1 0 0) by molecular beam epitaxy

Low-temperature molecular beam epitaxy was employed to grow Ge1−xSnx/Ge strained-layer superlattices (SLSs) on Si(1 0 0) substrates with a Ge buffer layer. The Ge1−xSnx and Ge layers in the SLSs were deposited at the same temperature as low as 180 °C. Surface roughening during the growth was investigated by in situ reflection high-energy electron diffraction (RHEED). The periods, compositions, and quality of the SLSs were characterized by high resolution X-ray diffraction (HR-XRD), random and aligned Rutherford backscattering spectra (RBS), transmission electron microscopy (TEM), and scanning TEM. Besides, a Ge1−xSnx/Ge SLS sample was grown directly on Si(1 0 0) for comparison. It's found that the quality of the Ge1−xSnx/Ge SLSs grown on a Ge buffer was significantly better than that grown directly on Si(1 0 0) substrate.