Fabrication of high-Ge-content silicon-Germanium film on SiO2/Silicon (111) patterned substrate by epitaxial lateral overgrowth

In this study, we achieved a high-Ge-content SiGe-on-Si heteropitaxial structure by utilizing the patterned SiO 2 /Si(111) substrate (PS) with micron-level line window array in the SiO 2 masking film and conducting the selective growth by liquid phase epitaxy (LPE). The anisotropic growth rate of LPE initially facilitated the epitaxial lateral overgrowth (ELO) of a low-Ge-content (20–25 %) SiGe buffer layer on PS. Subsequently, the heteroepitaxial growth of high-Ge-content (>95 %) SiGe progressed vertically through a composition self-modulation process. Atomic force microscope (AFM) analysis results demonstrated that the use of PS enables the surface roughness of high-Ge-content layer to decrease to as low as 2.1 nm, more than an order of magnitude better than grown directly on Si substrate. High content of Ge and the surface stress distribution in SiGe epitaxial layer were recognized by a Raman spectrometer. Furthermore, the conversion of elemental content from Si-rich to Ge-rich, and ultimately to a high-Ge-content (>95 %) state was distinctly illustrated by the cross-sectional energy dispersive X-ray spectroscopy (EDS). Besides, high-resolution X-ray diffraction (HR-XRD) analysis and room-temperature photoluminescence (PL) measurements were also conducted to confirm the sample quality. Finally, transmission electron microscopy (TEM) analysis indicated that the planar defects (microtwins/stacking faults) that frequently appear when the heteroepitaxial growth is performed directly on Si(111) face seem to be completely suppressed when it is performed on PS. Our film characterizations demonstrated that using PS to perform ELO by LPE can effectively limit the formation and propagation of threading dislocations caused by the lattice mismatch. Both the surface morphology and crystalline quality have thus been definitely improved for the heteroepitaxial layer prepared. Therefore, the present work might provide an effective method for preparing high-quality Ge-on-Si epitaxial structures and opened up a potential application path for advanced semiconductors.