A novel three-layer graded SiGe strain relaxed buffer for the high crystal quality and strained Si0.5Ge0.5 layer epitaxial grown

In this work, a novel three-layer SiGe strain relaxed buffer/strained Si0.5Ge0.5 layer stacking structure is systematically investigated. The novel three-layer graded SiGe strain relaxed buffer, whose Ge concentration increased from bottom to top by roughly 10% with an in situ annealing after each layer grown, can effectively constrain the threading dislocation in the strain relaxed buffer layer. Moreover, a chemical mechanical planarization process can be applied to the strain relaxed buffer to further improve its surface roughness. A high crystal quality and atomically smooth surface Si0.5Ge0.5 layer can be successfully realized on the novel chemical mechanical planarization-treated three-layer SiGe strain relaxed buffer. This strategy can attain at least 50 nm and 0.6% compressive strained Si0.5Ge0.5 layer and its quantification of the strain level is confirmed by utilizing the scanning moiré fringe imaging technique. It can be seen that this novel structure can provide a better mobility and larger width for the FinFET or nanowire SiGe channel device.