Stability of strain in Si layers formed on SiGe/Si(110) heterostructures

Strained Si/relaxed SiGe heterostructures grown on Si(110) substrates are attractive as a platform for high-hole-mobility Si-wafer-based electronic devices. The thickness of the strained Si has an impact on the performances of devices since the influence of the states at the Si/SiGe interface and the density of the diffused Ge atoms in the channel region can be suppressed by increasing the strained Si thickness. In this study, the critical layer thickness of a solid-source molecular beam epitaxy (MBE) grown strained Si film on a SiGe/Si(110) heterostructure with a Ge composition of about 30% was investigated by using polarized micro-Raman spectroscopy. Evolution of the surface morphology with the growth of the strained Si layer was also studied using atomic force microscopy. As a result, it is concluded that a nearly 70 nm thick smooth and anisotropically strained Si film can be formed on a Si_0.7Ge_0.3/Si(110) heterostructure by using the solid-source MBE method. (paper)