Relaxed Ge0.9Si0.1 alloy layers with low threading dislocation densities grown on low-temperature Si buffers

Relaxed ${\mathrm{Ge}}_x{\mathrm{Si}}_{\text{1−x}}$ epilayers with high Ge fractions but low threading dislocation densities have been successfully grown on Si (001) substrate by employing a stepped-up strategy and a set of low-temperature ${\mathrm{Ge}}_y{\mathrm{Si}}_{\text{1−y}}$ buffers. We show that even if the Ge fraction rises up to 90%, the threading dislocation density can be kept lower than ${\text{5×10}}^6\hspace{0.17em}{\mathrm{cm}}^{\mathrm{-2}}$ in the top layers, while the total thickness of the structure is no more than 1.7 μm.