Ge-on-Si: Single-Crystal Selective Epitaxial Growth in a CVD Reactor

A standard Si/SiGe ASM CVD reactor that was recently modified for merging GaAs and Si epitaxial growth in one system is utilized to achieve intrinsic and doped epitaxial Ge-on-Si with low threading dislocation and defect densities. For this purpose, the system is equipped with 2% diluted GeH4 as the main precursor gas for Ge deposition; and 0.7% diluted AsH3 and B2H6 precursor gases as well as a TriMethylGallium (TMGa) bubbler system for As, B and Ga doping of epitaxial Ge, respectively. The quality of Ge epitaxy on Si is investigated by plan-view and cross-sectional transmission electron-microscopy (TEM) and atomic-force microscopy (AFM) analysis.