Size dependence of hall mobility and dislocation density in Ge heteroepitaxial layers grown by MBE on a SiO₂ patterned Si template

We have investigated the size dependent properties of the Hall mobility and etch pit dislocations (EPDs) in germanium (Ge) heteroepitaxial layers. Pure Ge thin films were grown by molecular beam epitaxy (MBE) using pattern guided growth at 650 °C and compared with homoepitaxially grown films. The results show enhanced Hall mobility and lower dislocation density as the pattern size decreases. The number of EPDs was decreased by one order of magnitude and the Hall mobility measured with different sizes of van der Pauw patterns was enhanced by two times as the pattern size was decreased from 200×200 μm² to 3×3 μm². Raman spectroscopy was also employed to characterize residual strain and crystalline quality of the epitaxial films with respect to the pattern size. We conclude that nano-scale pattern guided heteroepitaxial growth of Ge may be a plausible method for monolithic integration of Ge optoelectronic or electronic devices onto a Si substrate.